EMC E20-585 Practice Test Questions, EMC E20-585 Exam Dumps

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Your Guide to the E20-585 Exam - Information Infrastructure

The E20-585 exam, also known as the Storage and Information Infrastructure Expert Exam for EMCIE, was a foundational certification in the EMC Proven Professional program. This exam was designed for technology professionals seeking to validate their comprehensive understanding of storage concepts, principles, and technologies that form the basis of a modern data center. Passing this exam demonstrated a candidate's expertise in the core elements of information storage and management, making it a valuable credential for storage administrators, architects, and anyone involved in the design and management of IT infrastructure.

The scope of the E20-585 exam was intentionally broad, covering the entire spectrum of storage and information infrastructure. It began with the fundamental concepts of data and information, moved through the detailed architecture of intelligent storage systems, and explored the various storage networking technologies like Fibre Channel SAN, IP SAN, and NAS. The exam also placed a strong emphasis on critical business functions such as backup and recovery, business continuity, and storage security. It was a true test of a professional's holistic understanding of the storage domain.

This five-part series will serve as a detailed guide to the key knowledge areas covered in the E20-585 exam. We will systematically break down each major topic, from the components inside a disk drive to the high-level concepts of disaster recovery planning. The goal is to provide a structured learning path that builds from foundational principles to complex architectures. For professionals studying the evolution of data center technologies or for those tasked with managing established storage systems, this content provides a deep and organized overview.

Preparing for the E20-585 exam required more than memorizing technical specifications; it demanded an understanding of the business drivers behind storage technology. The questions were often scenario-based, asking a candidate to choose the appropriate technology or architecture to solve a specific business problem, such as meeting a certain recovery time objective or securing a particular type of data. This series will focus on providing that crucial context, explaining not just what a technology is, but why it is important and where it fits into the larger IT strategy.

The Evolution to an Information-Centric Architecture

A central theme of the E20-585 exam was the understanding of the shift from a server-centric to an information-centric IT architecture. In the traditional server-centric model, storage was an internal component of a server. This model, known as Direct-Attached Storage (DAS), was simple and inexpensive but created significant problems as organizations grew. Each server became a silo of information, making it difficult to share data, manage storage centrally, or utilize storage resources efficiently. Data was effectively trapped inside the server that created it.

The information-centric architecture addresses these limitations by decoupling storage from the server. In this model, storage is externalized into a centralized, shared platform, typically a storage area network (SAN) or network-attached storage (NAS) system. This creates a flexible pool of storage resources that can be accessed by multiple servers. This shift was a key enabler for many of the technologies covered in the E20-585 exam, including virtualization, data mobility, and centralized data protection.

The benefits of an information-centric model are numerous. It improves storage utilization, as resources can be provisioned to servers on an as-needed basis from a shared pool. It simplifies management, as all storage can be managed from a single console. It enhances data availability and protection, as advanced features like replication and snapshots can be implemented at the storage system level. The E20-585 exam required a clear understanding of these benefits and how they address the challenges of the older, server-centric model.

This architectural shift also changed the role of the IT administrator. Instead of managing individual servers and their internal disks, the focus moved to managing information as a strategic asset. The administrator of an information infrastructure is concerned with the availability, performance, security, and protection of the organization's data, regardless of which server or application is currently using it. This holistic view of information management was a core concept for the E20-585 exam.

Core Components of a Data Center

The E20-585 exam required a foundational understanding of the five core components that make up a data center's physical infrastructure. These components must work together to provide the services that run an organization's business applications. The first, and most obvious, component is the set of application servers. These are the compute resources that run the business applications, whether they are physical servers or virtual machines.

The second core component is the network. The data center network provides the communication pathways between the servers and between the servers and the end-users. This includes the local area network (LAN) that connects the servers and other devices within the data center. The third component is the storage system. This is where the organization's data is stored and managed. As we've discussed, this is typically an external, shared storage platform.

The fourth component, and a key focus for the E20-585 exam, is the storage network. This is a separate, dedicated network that provides the connectivity between the application servers and the storage system. For a SAN, this would be a Fibre Channel or an Ethernet network. For a NAS, this is typically part of the main LAN. The fifth and final core component is the set of data center management tools. These are the software applications used to monitor, manage, and provision all the other components in the data center.

A well-architected data center ensures that these five components are in balance. A bottleneck in any one area, such as an under-provisioned storage network or an overloaded storage system, will impact the performance of the entire application environment. The E20-585 exam expected a candidate to understand the role of each of these components and how they interrelate to form a complete and functional information infrastructure.

An Introduction to Storage Architectures

A major part of the E20-585 exam was dedicated to the three primary storage architectures: Direct-Attached Storage (DAS), Network-Attached Storage (NAS), and Storage Area Network (SAN). DAS is the simplest model, where storage devices are directly connected to a single server. This can be an internal hard drive or an external enclosure connected via an interface like SAS or SCSI. While easy to deploy, DAS suffers from scalability limitations and creates the information silos discussed earlier.

Network-Attached Storage (NAS) provides a solution for file-level data sharing. A NAS device is a dedicated file server that connects to the main data center LAN. Servers and clients can then access the data on the NAS device using file-sharing protocols like CIFS (for Windows environments) or NFS (for Unix/Linux environments). From the perspective of the clients, the NAS device appears as a simple file share. The E20-585 exam required a clear understanding of NAS as a file-based storage solution.

Storage Area Network (SAN) provides a solution for block-level data access. A SAN is a dedicated, high-speed network that connects servers to a shared pool of storage. The servers see the storage presented by the SAN as if it were a local disk drive. This allows for high-performance, block-level access, which is required by many enterprise applications and databases. The E20-585 exam required a deep understanding of SAN as a block-based storage solution.

The key difference between NAS and SAN, and a critical concept for the E20-585 exam, is how the data is accessed. NAS presents data as files and folders, while a SAN presents data as raw disk blocks. This fundamental difference determines which applications are best suited for each architecture. File servers and web servers are a good fit for NAS, while databases and virtualization environments typically require the performance and block-level access of a SAN.

Data, Information, and Storage Tiers

The E20-585 exam required a clear understanding of the distinction between data, information, and storage. Data can be defined as raw, unprocessed facts. In the context of IT, this is the raw binary 1s and 0s that are stored on a disk. By itself, raw data has no meaning. Information is data that has been processed, organized, and put into a context to make it meaningful. For example, a list of numbers is data; a sales report that organizes those numbers by region and date is information.

Storage is the medium on which the data is recorded and stored. A key concept in modern storage management, and a topic for the E20-585 exam, is tiered storage. Not all data has the same value to an organization, and not all data has the same performance or availability requirements. Tiered storage is the practice of aligning the cost of the storage media with the value of the data being stored on it.

This typically involves creating several tiers of storage. Tier 1 would be the highest performance and most expensive storage, built with technologies like solid-state drives (SSDs). This tier would be used for mission-critical applications that require the fastest response times, such as a transactional database. Tier 2 might use high-performance hard disk drives (HDDs) for less critical applications. Tier 3 might use lower-cost, high-capacity HDDs for data that is accessed less frequently, such as file shares or backups.

The goal of a tiered storage strategy is to optimize both performance and cost. By placing the right data on the right tier at the right time, an organization can meet its service level agreements (SLAs) without overspending on high-performance storage for all of its data. The E20-585 exam required an understanding of this concept and the technologies that enable it, such as automated storage tiering, which can automatically move data between tiers based on its activity level.

Disk Drive Components and Performance

A deep understanding of the underlying storage media was a fundamental requirement for the E20-585 exam. The most common storage medium at the time was the hard disk drive (HDD). An HDD is an electromechanical device that stores data on rotating magnetic platters. The exam required knowledge of the key components of an HDD, including the platters, the read/write heads, the actuator arm assembly, and the spindle motor that spins the platters.

The performance of an HDD is determined by several factors. The rotational speed of the platters, measured in revolutions per minute (RPM), is a major factor; faster RPMs result in lower rotational latency. The second key factor is the seek time, which is the time it takes for the actuator arm to move the read/write heads to the correct track on the platter. The total time to service a random I/O request is largely a function of these two mechanical latencies. The E20-585 exam expected a clear understanding of these performance characteristics.

In contrast to HDDs, solid-state drives (SSDs) were an emerging technology covered in the E20-585 exam. An SSD is a non-volatile storage device that uses flash memory to store data. Because SSDs have no moving parts, they do not suffer from the mechanical latencies of an HDD. This allows them to provide dramatically better performance, especially for random I/O workloads, and much lower response times.

The E20-585 exam required you to understand the trade-offs between HDDs and SSDs. HDDs offered a lower cost per gigabyte and were available in very large capacities, making them ideal for storing large amounts of less active data. SSDs offered much higher performance but at a significantly higher cost per gigabyte. This cost and performance difference is the primary driver behind the tiered storage strategies that are a key part of modern storage infrastructure.

The Architecture of an Intelligent Storage System

The E20-585 exam moved beyond individual disk drives to cover the architecture of an intelligent storage system, also known as a storage array. An intelligent storage system is much more than just a box of disks (a JBOD). It is a specialized, high-performance computer whose sole purpose is to store and manage data. These systems provide advanced features like caching, RAID protection, and centralized management that are not available with simple direct-attached storage.

An intelligent storage system has three key components. The first is the front-end. The front-end consists of a set of controllers and ports that provide the connectivity to the application servers. These front-end ports are what the servers connect to, using protocols like Fibre Channel or iSCSI. The front-end controllers are responsible for receiving the I/O requests from the servers. The E20-585 exam required a solid understanding of the role of the front-end in providing host connectivity.

The second key component is the cache. The cache is a large amount of very fast, volatile memory (RAM) within the storage system. It is used to temporarily store data that is being read from or written to the disks. The cache is the single most important factor in the performance of an intelligent storage system. By servicing I/O requests from the high-speed cache instead of the slower mechanical disks, the system can provide very low latency and high throughput.

The third component is the back-end. The back-end consists of a set of controllers and ports that provide the connectivity to the physical disk drives. The back-end controllers are responsible for managing the RAID groups, performing the reads and writes to the disks, and managing the overall health of the storage pool. The E20-585 exam required a clear understanding of how these three components—front-end, cache, and back-end—work together to provide a high-performance, highly available storage service.

Understanding RAID (Redundant Array of Independent Disks)

RAID is one of the most fundamental technologies in data storage, and it was a major topic on the E20-585 exam. RAID is a technique that combines multiple physical disk drives into a single logical unit to provide benefits in terms of performance, data protection, or both. There are several different RAID levels, each with its own specific characteristics and trade-offs. A deep understanding of the most common RAID levels was an absolute requirement for the exam.

RAID 0, also known as striping, provides the highest performance but offers no data protection. In RAID 0, data is broken into blocks, or stripes, and written across all the disks in the array. This allows multiple disks to service a single I/O request, which dramatically increases performance. However, if any single disk in a RAID 0 set fails, all the data in the set is lost.

RAID 1, also known as mirroring, provides the highest level of data protection but is the least efficient in terms of capacity. In RAID 1, all data that is written to one disk is also simultaneously written to another disk, creating an exact copy or mirror. If one disk fails, the system can continue to operate using the data on the other disk. The downside is that you need twice as much raw disk capacity as the amount of usable capacity you get.

The most common RAID levels used in enterprise storage systems are RAID 5 and RAID 6. These are parity-based RAID levels that provide a balance of performance, capacity, and protection. The E20-585 exam required a detailed understanding of how parity works. In RAID 5, a calculated parity block is written for each stripe of data. If a single disk fails, the data on that disk can be rebuilt using the parity information from the other disks. RAID 6 uses two parity blocks, allowing it to withstand the failure of two disks simultaneously.

Nested RAID Levels and Hot Spares

In addition to the basic RAID levels, the E20-585 exam also covered nested, or hybrid, RAID levels. These RAID levels combine two of the basic RAID levels to gain the benefits of both. The most common nested RAID level is RAID 1+0 (also known as RAID 10). A RAID 1+0 set is created by first creating several mirrored pairs of disks (RAID 1) and then striping the data across all of these pairs (RAID 0).

RAID 1+0 offers the best of both worlds: it provides the high performance of striping and the high data protection of mirroring. It can withstand the failure of one disk in any of its mirrored pairs. The performance of RAID 1+0 is particularly good for write-intensive workloads, as it does not have the "write penalty" associated with parity-based RAID levels. The main drawback of RAID 1+0 is its high capacity overhead; like RAID 1, it requires twice as much raw capacity as usable capacity. The E20-585 exam required you to understand these trade-offs.

Another important concept related to RAID is the hot spare. A hot spare is an idle disk drive that is part of the storage system but is not part of any active RAID group. It is kept online and ready to be used. If a disk in a RAID group fails, the storage system can automatically use the hot spare to start rebuilding the failed disk's data. This significantly reduces the time that the RAID group is in a degraded and vulnerable state.

The 9A0-086 exam expected a practical understanding of how hot spares are used. Configuring the correct number of hot spares is a key part of designing a resilient storage environment. The general rule is to have at least one hot spare for a certain number of active disks, with the ratio depending on the service level requirements of the data being stored.

Storage Provisioning Techniques

Once a RAID group is created, the storage within it needs to be provisioned to the application servers. The E20-585 exam covered the different methods for doing this. The traditional method of provisioning is to create a logical unit, or LUN, of a specific size from the RAID group. A LUN is a logical representation of a disk drive. This LUN is then assigned to a specific server. From the server's perspective, the LUN appears as a raw, unformatted disk drive that it can then partition and format with a file system.

A more modern and flexible approach covered in the E20-585 exam is virtual provisioning, also known as thin provisioning. In traditional, or "thick," provisioning, all the storage capacity for a LUN is allocated upfront from the RAID group at the time the LUN is created. With thin provisioning, the storage is allocated on-demand as data is actually written by the server.

Thin provisioning offers significant benefits in terms of storage utilization. You can present a server with a LUN that is much larger than the physical capacity that has actually been allocated to it. This allows you to oversubscribe your storage pool, which can lead to significant cost savings and can simplify capacity management. The E20-585 exam required an understanding of both the benefits and the risks of thin provisioning. The main risk is that if all the thinly provisioned LUNs try to grow at the same time, you could run out of physical capacity in the storage pool.

In addition to LUNs, some storage systems use the concept of a metaLUN. A metaLUN is a way to combine multiple LUNs together to create a single, larger logical unit. This was a technique used to overcome the size limitations of individual LUNs or to improve performance by spreading the workload over more physical disks. A solid grasp of these different provisioning techniques was a key part of the E20-585 exam.

Introduction to Fibre Channel SAN

A major part of the E20-585 exam was dedicated to Storage Area Networks (SANs), and the most prevalent type of SAN at the time was the Fibre Channel (FC) SAN. A Fibre Channel SAN is a dedicated, high-speed network whose sole purpose is to connect servers to storage systems. It uses the Fibre Channel protocol, which was specifically designed for storage traffic, to provide reliable, low-latency, block-level access to data. This high performance makes FC SAN the ideal choice for mission-critical, transactional applications like large databases.

The physical components of an FC SAN were a key topic for the E20-585 exam. The first component is the Host Bus Adapter (HBA). This is a card that is installed in each server and provides the physical connectivity to the Fibre Channel network. Each HBA port has a unique 64-bit identifier called a World Wide Name (WWN), which is similar to a MAC address on an Ethernet network card.

The second key component is the Fibre Channel switch. The switches form the fabric of the SAN. All the servers and the storage systems are connected to the ports on these switches. The switches are responsible for routing the traffic between the servers and the storage. For high availability, it is a standard best practice to build a SAN with at least two separate switches, creating two redundant fabrics. Each server and storage system would then have a connection to each fabric.

The final component is the storage system itself, which has front-end Fibre Channel ports that connect to the SAN switches. The E20-585 exam required a clear understanding of how these three components—HBAs, switches, and the storage array—work together to create a complete storage network. This includes understanding the different types of cabling (optical fiber) and the different port speeds that were common at the time, such as 4Gb/s and 8Gb/s.

The Fibre Channel Protocol Stack

While the E20-585 exam was not a deep protocol-level exam, it did require a conceptual understanding of the Fibre Channel protocol stack. The FC protocol is defined as a layered model, similar to the OSI model for networking. This layered approach allows for modularity and interoperability between different vendors' equipment. The exam expected a high-level knowledge of the different layers and their primary functions.

The lowest layers, FC-0 and FC-1, define the physical aspects of the network, such as the cabling, connectors, and the encoding of signals on the wire. The FC-2 layer is one of the most important. It is the framing and flow control layer. This layer is responsible for breaking the data into frames, addressing the frames to their destination, and managing the flow of traffic to prevent congestion.

The FC-4 layer is the upper layer protocol mapping layer. This is the layer that maps the upper-level protocols, such as the SCSI command set, onto the lower-level Fibre Channel frames. When a server wants to read a block of data from the storage system, it sends a SCSI command. The FC-4 layer encapsulates this SCSI command into Fibre Channel frames so that it can be transported across the SAN. The E20-585 exam required an understanding that Fibre Channel is essentially a transport mechanism for the SCSI protocol.

The interaction between these layers enables the high performance and reliability of an FC SAN. The protocol was designed from the ground up for storage traffic, with features like credit-based flow control to ensure lossless data delivery. A conceptual grasp of this protocol stack was a key part of understanding why Fibre Channel was the dominant technology for enterprise SANs and a core topic for the E20-585 exam.

Zoning and LUN Masking in a SAN

Securing a SAN and ensuring that servers can only access the storage that has been assigned to them is a critical function of a storage administrator. The E20-585 exam placed a strong emphasis on the two primary security mechanisms used in a Fibre Channel SAN: zoning and LUN masking. These two technologies work together to provide a robust, multi-layered security model for the storage network.

Zoning is a function that is performed on the Fibre Channel switches. A zone is a logical grouping of devices, typically a server's HBA ports and the storage system's front-end ports, that are allowed to communicate with each other. Devices that are not in the same zone cannot see each other or communicate with each other. This is a fundamental security mechanism that prevents a server from accidentally or maliciously accessing another server's storage traffic. The E20-585 exam required you to know the different types of zoning, such as WWN zoning, which is the most common and secure method.

While zoning controls which devices can see each other, LUN masking controls which LUNs (logical units) a server can see on a storage system. LUN masking is a function that is performed on the storage system itself. After a zone has been created to allow a server to see the storage system, the administrator must then configure LUN masking to specify exactly which LUNs that server is allowed to access.

This two-layered approach provides a very secure environment. Zoning provides security at the network fabric level, while LUN masking provides security at the storage system level. A typical workflow would be to first create a zone containing the server's WWNs and the storage system's WWNs, and then go to the storage system and create a storage group that maps the desired LUNs to the server's WWNs. A solid understanding of this entire workflow was a key requirement for the E20-585 exam.

IP SAN: iSCSI and FCIP

While Fibre Channel was the dominant SAN technology, the E20-585 exam also covered the use of standard IP networks for building a SAN. This is known as an IP SAN. The primary protocol for IP SAN is iSCSI (Internet Small Computer System Interface). iSCSI is a protocol that encapsulates SCSI commands into standard TCP/IP packets. This allows block-level storage traffic to be transported over a standard Ethernet network using standard network switches and adapters.

The key benefit of iSCSI is its lower cost and complexity compared to Fibre Channel. Since it uses standard Ethernet, organizations can leverage their existing network infrastructure and expertise instead of having to invest in a separate, dedicated Fibre Channel network. The E20-585 exam required an understanding of the components of an iSCSI SAN. On the server side, you use an iSCSI initiator, which can be a standard network card with a software initiator or a specialized iSCSI HBA. The storage system has front-end ports that act as the iSCSI target.

Another important IP-based storage protocol covered in the E20-585 exam is FCIP (Fibre Channel over IP). FCIP is a tunneling protocol that is used to connect two separate Fibre Channel SANs over a long distance using an IP network. It is not used for connecting a server directly to storage, but rather for connecting two SAN fabrics together for disaster recovery purposes. FCIP encapsulates the entire Fibre Channel frame into an IP packet, allowing the two SANs to appear as one logical fabric, even if they are hundreds of miles apart.

The E20-585 exam required you to understand the different use cases for iSCSI and FCIP. iSCSI is an alternative to Fibre Channel for building a primary SAN, and it is a popular choice for small to medium-sized businesses or for less performance-sensitive applications. FCIP is a specialized protocol used for long-distance SAN extension and remote replication, a key part of business continuity.

Network Attached Storage (NAS)

In addition to the block-based SAN technologies, the E20-585 exam also required a comprehensive understanding of Network Attached Storage (NAS). As discussed earlier, NAS is a file-level storage architecture. A NAS device, often called a filer, is a specialized file server that is connected to the LAN. It provides storage to clients and servers in the form of file shares. This is different from a SAN, which provides storage in the form of raw disk blocks.

The components of a NAS environment are simple. You have the NAS device itself, which contains the storage and the software that manages the file systems and the file sharing protocols. This device is connected to the same Ethernet LAN as the clients and servers that need to access the data. The clients then connect to the NAS device using a standard file sharing protocol. The E20-585 exam required you to know the two primary NAS protocols.

The first protocol is CIFS (Common Internet File System), which is the standard protocol used by Windows environments. A Windows client can map a drive letter to a CIFS share on a NAS device, and it will appear and behave just like a local drive. The second protocol is NFS (Network File System), which is the standard protocol used in Unix and Linux environments. An NFS client can mount a file system from a NAS device, and it becomes part of the client's local directory tree.

The E20-585 exam required a clear understanding of the use cases for NAS. It is an ideal solution for consolidating file servers, for providing home directories for users, and for any application that needs to share data at the file level. Some NAS devices, known as unified storage systems, can also provide block-level access via iSCSI or Fibre Channel, blurring the lines between NAS and SAN and providing a single platform for all of an organization's storage needs.

Introduction to Data Protection

A central theme of the E20-585 exam and a critical function of any IT organization is data protection. Data protection is the process of protecting data from loss and ensuring that it can be recovered in the event of a failure or disaster. The most common and fundamental form of data protection is backup. A backup is a copy of data that is taken and stored in a separate location so that it can be used to restore the original data in case it is lost or corrupted.

The E20-585 exam required a deep understanding of the key concepts and terminology of backup and recovery. Two of the most important metrics are the Recovery Point Objective (RPO) and the Recovery Time Objective (RTO). RPO defines the amount of data loss that a business can tolerate. For example, an RPO of 24 hours means that the business can afford to lose up to 24 hours worth of data. This metric drives the frequency of backups.

RTO defines how quickly a business needs to be able to recover its data and resume operations after a failure. An RTO of 4 hours means that the systems must be back online within 4 hours. This metric drives the choice of backup and recovery technology. A lower RTO requires a faster recovery solution. The E20-585 exam expected you to be able to apply these concepts to a given business scenario.

The backup and recovery process is a key part of an organization's overall Business Continuity plan. Business Continuity is a broader concept that includes all the processes and procedures that an organization puts in place to ensure that its critical business functions can continue to operate during and after a disaster. A solid backup and recovery strategy is the technological foundation of any good Business Continuity plan.

Backup Architecture and Components

The E20-585 exam required a detailed understanding of the components that make up a typical backup environment. The first and most central component is the backup server. The backup server is a machine that runs the backup software. It is responsible for managing the entire backup process, including scheduling the backups, managing the backup catalog (a database that keeps track of what has been backed up and where it is stored), and controlling the backup devices.

The second component is the backup client, also known as a backup agent. This is a piece of software that is installed on the application servers that need to be backed up. The backup agent is responsible for reading the data from the application server and sending it across the network to the backup server or the backup storage device. There are often specialized agents for different applications, such as a database or an email server, that can properly back up the application's live data.

The third component is the backup storage, also known as the backup target or media. This is where the backup data is actually stored. In the era of the E20-585 exam, the most common backup medium was magnetic tape, stored in a tape library. A tape library is an automated device that contains multiple tape drives and a robotic arm to move the tapes between the drives and the storage slots. Disk-based backup systems were also becoming very popular, offering much faster backup and recovery performance.

These components work together to form the backup infrastructure. The backup server instructs the backup client on an application server to start a backup. The client reads the data and sends it over the network to the backup server, which then writes the data to the tape or disk storage. The E20-585 exam required a clear understanding of the roles of each of these components and how they interact.

Backup Methods and Strategies

There are several different methods for performing a backup, and the E20-585 exam required a comprehensive knowledge of them. The most basic type of backup is a full backup. A full backup, as the name implies, is a complete copy of all the data that is selected for backup. Full backups are the simplest to manage and provide the fastest recovery time, as you only need to restore from a single backup set. However, they are also the most time-consuming to perform and require the most storage capacity.

To reduce the time and storage required for backups, most organizations use a combination of full backups and incremental or differential backups. An incremental backup only backs up the data that has changed since the last backup of any type (full or incremental). This results in a very fast backup process and uses a minimal amount of storage. However, a full restore can be complex, as you need to restore the last full backup and then all the subsequent incremental backups in order.

A differential backup backs up all the data that has changed since the last full backup. The daily differential backups will grow larger throughout the week, but the restore process is simpler than with incrementals. To perform a full restore, you only need to restore the last full backup and the last differential backup. The E20-585 exam required a clear understanding of the trade-offs between these different methods in terms of backup time, storage usage, and restore complexity.

A common backup strategy is to perform a full backup once a week (e.g., on the weekend) and then either an incremental or a differential backup every night on the weekdays. This provides a good balance of performance and manageability. The choice between incremental and differential depends on the specific RPO and RTO requirements of the business.

Data Deduplication

A revolutionary technology in the backup and recovery space, and a key topic for the E20-585 exam, was data deduplication. Data deduplication is an intelligent compression technique that eliminates redundant data from a backup set. In a typical enterprise environment, much of the data that is backed up is redundant. For example, many users might have the same operating system files on their servers, or the same presentation might be stored in multiple users' home directories.

A deduplication system works by breaking the backup data stream into small chunks. For each chunk, it calculates a unique signature, or hash. It then checks a central index to see if it has ever seen a chunk with that same signature before. If it has, it does not store the chunk again; it simply stores a small pointer to the existing chunk. If the chunk is new, it is stored, and its signature is added to the index.

This process can result in dramatic reductions in the amount of storage required for backups, often by a factor of 20 to 1 or even more. The E20-585 exam required an understanding of the different places where deduplication can be performed. Source-based deduplication is performed by the backup agent on the application server before the data is sent over the network. Target-based deduplication is performed by the backup appliance or server after the data has been received.

Data deduplication not only saves storage capacity, but it can also improve backup performance by reducing the amount of data that needs to be sent over the network. It was a transformative technology that made disk-based backup much more cost-effective than tape. A solid understanding of the principles and benefits of data deduplication was a key part of the E20-585 exam.

Backup vs. Archiving

A common point of confusion, and a distinction that was important for the E20-585 exam, is the difference between backup and archiving. While both involve making a copy of data, they have very different purposes, and they are driven by different business requirements. A backup is a copy of data that is made for the purpose of recovery in the event of a data loss event. The primary driver for backup is business continuity and disaster recovery.

An archive, on the other hand, is a repository for data that is no longer in active use but must be retained for long-term storage. The primary drivers for archiving are typically regulatory compliance and legal discovery. Many industries have regulations that require data to be kept for a certain number of years. An archive provides a cost-effective and searchable repository for this data.

Another key difference is in the way the data is managed. After data is backed up, the original data is typically left in place on the primary storage system. After data is moved to an archive, the original copy is often deleted from the primary storage system to free up space. This is a key benefit of archiving, as it helps to control the growth of primary storage.

The E20-585 exam required a clear understanding of these distinctions. A backup solution is optimized for fast recovery and is based on RPO and RTO. An archiving solution is optimized for long-term retention, searchability, and authenticity, and it is based on compliance and legal requirements. While some technologies can be used for both, they are two distinct business processes with different goals.

Introduction to Business Continuity

The E20-585 exam extended beyond simple backup to cover the broader and more strategic concept of Business Continuity (BC). Business Continuity is a proactive process that ensures an organization's critical business functions can continue to operate during and after a disruptive event, such as a natural disaster, a power outage, or a major hardware failure. It is a comprehensive plan that involves people, processes, and technology. A key technology enabler for Business Continuity is disaster recovery.

Disaster Recovery (DR) is the reactive component of Business Continuity. It is the set of technologies and procedures that are used to recover the IT infrastructure and data at a secondary location if the primary data center becomes unavailable. The E20-585 exam required a deep understanding of the key metrics that drive a DR strategy, which are the Recovery Point Objective (RPO) and the Recovery Time Objective (RTO), as discussed in the context of backup.

A DR plan involves having a secondary data center site that is geographically separate from the primary site. The data from the primary site must be replicated to the secondary site. In the event of a disaster at the primary site, the business can failover its operations to the secondary site and continue to function. The E20-585 exam covered the various technologies that are used to achieve this data replication and failover.

The goal of a Business Continuity and Disaster Recovery plan is to minimize the financial and operational impact of a disaster. The level of investment in a DR solution is typically driven by a Business Impact Analysis (BIA), which is a formal process for identifying the critical business functions and the potential impact of their disruption. This business-centric view of data protection was a key part of the E20-585 exam.

Remote Replication Technologies

The core technology that enables a disaster recovery solution is remote replication. Remote replication is the process of copying data from a storage system at a primary site to a storage system at a secondary site. The E20-585 exam required a detailed understanding of the different types of remote replication and their characteristics. The two main types are synchronous and asynchronous replication.

Synchronous remote replication provides the highest level of data protection, guaranteeing zero data loss (an RPO of zero). In a synchronous replication environment, when a server writes data to the primary storage system, the storage system will not acknowledge the write back to the server until it has been safely written to both the local cache and the cache of the remote storage system at the secondary site. This ensures that the two sites are always in perfect sync.

The main drawback of synchronous replication is that it is very sensitive to distance and network latency. Because the application has to wait for the write to be acknowledged from the remote site, any delay on the network will directly impact the application's performance. For this reason, synchronous replication is typically only used for shorter distances, usually within the same metropolitan area. The E20-585 exam required an understanding of this performance implication.

Asynchronous remote replication is used for longer distances. In an asynchronous environment, the primary storage system acknowledges the write back to the server as soon as it is written to its local cache. The data is then replicated to the remote site in the background at a later time. This means that asynchronous replication does not impact the application's performance, but it does introduce a potential for data loss (a non-zero RPO). The E20-585 exam required a clear understanding of the trade-offs between these two replication methods.

Disaster Recovery Solutions

The E20-585 exam required an understanding of how replication technologies are used to build different types of disaster recovery solutions. The choice of solution depends on the RPO and RTO requirements of the business. A simple DR solution might involve backing up data to tape and then physically shipping the tapes to an offsite location. This provides a very high RPO and RTO and is only suitable for non-critical data.

A more common solution for many businesses is a hot site DR model. In this model, the organization has a secondary data center with a pre-configured infrastructure of servers and storage. Data is replicated to this site using asynchronous replication. In the event of a disaster, the business would perform a failover, which involves bringing the applications online at the hot site using the replicated data. This can provide a reasonably low RTO, typically measured in hours.

For the most mission-critical applications that cannot tolerate any downtime or data loss, a high availability solution is required. This often involves a campus or metro-area cluster. In this model, two data centers are located a short distance apart and are connected by a high-speed, low-latency network. Data is replicated between the two sites using synchronous replication. The application servers are often clustered across the two sites, allowing for an automatic and near-instantaneous failover in the event of a failure at one site.

This type of solution can provide an RPO of zero and an RTO measured in minutes or even seconds. The E20-585 exam required you to be able to map these different DR solutions to specific business requirements for RPO and RTO. It was a key part of demonstrating an ability to apply storage technologies to solve business problems.

Storage Security Domains

Securing the storage infrastructure is just as important as securing the servers and the network. The E20-585 exam required a comprehensive understanding of the different security domains within a storage environment. A multi-layered security approach is needed to protect the confidentiality, integrity, and availability of an organization's data. This involves securing the management access, the host access, and the data itself.

The first domain is securing the management access to the storage infrastructure. This involves using strong passwords for all administrative accounts on the storage systems and the SAN switches. It is also a best practice to use role-based access control (RBAC) to give administrators only the permissions they need to perform their jobs. Access to the management interfaces should also be restricted to a dedicated management network.

The second domain is securing the host access to the data. As we discussed in the SAN section, this is achieved using a combination of zoning on the SAN switches and LUN masking on the storage system. These technologies ensure that a server can only access the specific storage LUNs that have been assigned to it. This is a fundamental security control that prevents unauthorized access to data from other servers on the SAN.

The third domain is securing the data itself. This can involve using data encryption. Data can be encrypted in-flight as it travels across the network, which is important for remote replication over an untrusted network. Data can also be encrypted at-rest on the storage media itself. This protects the data from being read if a disk drive is physically stolen from the data center. The E20-585 exam required an awareness of these different security domains and the technologies used to secure them.

Final Preparation

To successfully pass the E20-585 exam, a candidate needed a broad and foundational knowledge of all the topics covered in this series. The exam was designed to be a comprehensive test of a professional's understanding of the entire information storage and management landscape. The best preparation strategy would have been one that combined diligent study with a focus on understanding the underlying concepts rather than just memorizing facts.

The official curriculum and study materials from EMC were the most important resources for preparation. These materials were specifically designed to cover the exam objectives in detail. A thorough review of the official exam objectives was a crucial first step, as it provided a clear roadmap of all the topics that could be covered. This allowed a candidate to structure their study plan and identify any areas where they needed to focus more attention.

While hands-on experience with a specific storage system is always valuable, the E20-585 exam was largely vendor-neutral and focused on concepts and principles. Therefore, a key part of the preparation was to understand the "why" behind the technologies. Why is RAID 5 different from RAID 1+0, and what are the workload characteristics of each? What are the business drivers that would lead you to choose a synchronous replication solution over an asynchronous one? The exam heavily favored this type of conceptual and analytical thinking.

Finally, the E2t0-585 exam was a stepping stone in the EMC Proven Professional program. It was the foundation upon which more specialized, technology-specific certifications were built. A candidate who prepared for this exam by truly understanding the core principles of storage, networking, data protection, and security would not only be well-prepared to pass the exam, but would also have the essential knowledge needed to succeed in a career in the rapidly evolving world of information infrastructure.

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