How Data Recovery is Performed on Failed RAID 5 Arrays

How Data Recovery is Performed on Failed RAID 5 Arrays
By Andrea Stone

RAID 5 arrays are used for many applications because they are for the most part cost-effective and provide a level of fault tolerance not provided by some other levels of RAID. As with any RAID level, RAID 5 can experience many different types of problems. This article will provide a brief discussion of some of the problems causing RAID 5 failure and how data recovery can work to solve these problems.

Problems That Can Cause RAID 5 Failure

Bad Sectors

A RAID 5 can fail due to bad sectors on any of the disks in the array. This can force the array to go offline.

Corrupt Data

A RAID 5 can suffer from corrupt data due to many reasons including viruses, user error, overwriting files, and scratches on the surface of the disk platters.

Degraded RAID 5

A RAID 5 becomes degraded when there is a loss of one of the member disks. This causes a huge decrease in performance and also removes the fault tolerance of the RAID 5. Operating a degraded RAID 5 is dangerous because the loss of a second disk will cause the entire array to be lost.

Deleted Files

Many times a user will accidentally delete important data in a RAID 5 array. Other times, it is done intentionally by disgruntled employees. In most situations, deleted files can be recovered.

Missing Partitions

In many cases, the partition table can become corrupt or missing causing an entire partition to disappear or become unusable. This makes data recovery necessary. Attempting recovery with software will increase the risk of permanent data loss.

RAID 5 Controller Failure

A Hardware RAID 5 array uses a controller which contains all of the logic and handles the operations of the array. For many reasons, the array can experience a controller failure. This can cause the array to not boot. It could also cause the logical volume to disappear.

RAID 5 Disk Failure/RAID 5 Drive Failure

A RAID 5 is a set of three or more disk drives. Any of these drives can experience failure. A RAID 5 is configured with the ability to withstand the failure of only one disk at a time. In most cases, the RAID can be recovered in a data recovery lab using parity data written to the disks by the array. Even if more than one disk has failed, data recovery is still possible in a recovery lab.

RAID 5 Firmware Failure

Firmware problems can occur in the RAID controller or the member disk drives.

RAID 5 Rebuild Failure

For various reasons, a RAID 5 array can experience a rebuild failure. This may keep member disks offline and render the array unusable.

Server Crash

Many times, the host server experiences problems and can crash. This of course makes the array unaccessible. A data recovery lab can recover the data from the member disks.

How to Ensure RAID 5 Data Recovery is Successful

If you have experienced a RAID 5 failure, it is important that you do not take matters into your own hands. This can cause the parity data to be overwritten. Parity data, which is written to the member disks, is in many cases vital to ensure a successful recovery. The very first thing you should do is power off the RAID server immediately to ensure that no additional writes are performed. Any events describing what may have happened to cause the problem should be noted. If the member disk drives are removed from the server, they should be labeled in the correct order they were removed. The disk order is very important if time is of the essence. This is also important if you have a large number of member disks.

To ensure a successful data recovery, it is important that the failed RAID 5 remain intact. More information can be found by visiting [http://www.rewave.com/raid-5-recovery.htm ]RAID 5 recovery.

This article can be freely published on a website however it must not be modified in any way including the author bylines, and the hyperlink must be made active as shown below.

Andrea Stone is employed with ReWave Hard Drive Recovery, a data recovery company serving clients in cities worldwide including Atlanta, Charlotte, Dallas, Houston, Los Angeles, Memphis, Miami, Nashville, New Orleans, New York City, Orlando, Phoenix, Raleigh, Richmond, San Antonio, San Diego, and Tampa. Visit the [http://www.rewave.com]ReWave Hard Drive Recovery website for more information about RAID recovery and data recovery.

Article Source: http://EzineArticles.com/?expert=Andrea_Stone http://EzineArticles.com/?How-Data-Recovery-is-Performed-on
-Failed-RAID-5-Arrays&id=438410

Tape – Still The Best For Backup And Archiving

Tape is one of the real old die hards in the world of data storage and archiving. (Remember those shots of the Apollo mission when the fate of the astronauts was in the hands of those whirling spools of magnetic tape in mission control?) But with the introduction in recent decades of a slew of more modern media – optical discs, memory cards, and zip drives, for example, does plain old tape still have a role to play?

If you're a traditionalist, you'll be pleased to learn that the answer is an (almost) unqualified 'yes'. Tape's enduring popularity is due to the range of advantages it offers.

For one thing, using magnetic tape for backup is extremely cost effective. You can backup your entire server on one mid-range tape which costs around $20. Plus, magnetic tape can be re-used. So you can copy new information onto tapes from earlier backups. As your data grows and changes, you are always making new copies and are not overwhelmed with countless spools or reels of tape.

Then, there's magnetic tape's long archival stability. Tape is no longer stored on open reels but in hardy cartridge formats which include DLT and LTO. However, the fact remains that tape is a contact medium. So the resulting abrasion will ultimately wear the tape out. Nonetheless, the lifespan of tape compares favourably with other media. And consider this. Drop a tape on the floor from a few feet up, and then do the same with a disk. Which one is more likely to work well afterwards? I think you know the answer. The fact is that any medium can fail. In fact, recent research has revealed that the shelf life of optical media such as DVDs is far less than originally thought. In fact, well under a decade.

What's more, though tape is seen as an old technology, innovation has been going on. For example, the introduction of WORM (Write-Once-Read-Many) tape has provided additional security for data that is being stored for legal and compliance purposes.

Of course tape has its own foibles which need to be handled with care. For one thing, it is a thin plastic medium and so need to be stored in the right environment free from corrosive elements. A dedicated archival room is essential for effective storage.

And with regard to data recovery, you have to remember the following. Essentially, any data that has been overwritten is gone forever. A tape drive will not let you get to older data beyond the overwritten portion. However for tapes damaged by the elements, the scenario is more promising. Ultimately, though, the key to the recovery of tape data is an understanding the data that has been recovered, so the most powerful data recovery tool is the brain.

At the end of the day, every medium has it good and bad points. But magnetic tape's combination of economy, hardiness and re usability give it the edge you need to handle all your data backup needs. Tape for backup and archiving has already clicked up a half-century of solid use and looks set to be with us for another 50 years at least.

---

About the Author: Mark Sear has been working in the field of Data Recovery since 1984 and later formed Altirium, a company which offers tape recovery and data conversion services for tape, disk and all other computer storage media.

Tape Backup (part 1)

Given the importance of information and the potential high cost associated with data loss, reliable data protection has become an obligation, but backup and recovery seems very complicated and time consuming to undertake. Don't spend another day without protecting your valuable business data, or without understanding your options and what they mean. ³²

---

Wasabi Storage Builder for iSCSI is a fast, powerful, and cost-effective iSCSI Storage Area Network (SAN) solution. Built on Wasabi's industry-proven storage systems and software technologies, Storage Builder for iSCSI delivers top-notch features and performance at a price that's hard to beat.⁹

Traditional data protection tech-nologies, such as tape backup and fault-tolerant storage devices, protect business data from failures and human errors that can damage individual devices or buildings. However, corporate data is vulnerable to site- and region-wide disasters even if tape backup and RAID devices are both in place. Network data mirroring complements these traditional backup methods by protecting organizations from events that can destroy fault-tolerant storage devices. If your organization risks losing valuable time or business information due to wide-area disasters, network data mirroring may be a wise technology addition to your disaster recovery program.⁴⁴

Store one backup tape off site. This will ensure your files are preserved if your site experiences a fire, flood or other disaster. Some companies swap backup tapes with other offices. With some smaller businesses, it often makes sense for one employee to take the backup tape home with him. Another option is using an off-site storage firm that provides fire-protected storage facilities for print and digital media as well as tape.³

Instead of having folks pull tape cartridges for distribution to off-site storage, why not write your second tape copy directly to a remote vault across a network? Services exist, and have been discussed in this column, to facilitate that modus operandi. They will even send the tape electronically to your recovery center, if you prefer.¹⁷

---

Make sure you verify your backups. Most backup software will automatically do a quick "read-after-write" verification and will optionally do a full verification. The latter is more thorough and more time-consuming, roughly doubling the backup time.²⁴

There are a number of enterprise tape backup solutions, such as Sun StorEdge Enterprise Backup Software, VERITAS NetBackup, and LEGATO NetWorker, geared toward larger corporations. Many sites, especially smaller ones, don't wish to pay the license fees that some of these solutions command.⁹

Store your tapes properly. With backup tapes on site, keep them stored in a stable environment, without extreme temperatures, humidity or electromagnetism. Do not, for instance, store the tapes in a safe on the opposite side of the wall from a large generator, whose electrical fields can wreck havoc with the data on them.³

Tape backup involves the uses of tape drives that store data on magnetic tapes. The number of tapes required will depend on the capacity of the tapes as well as the amount of data stored on the computers that need to be backed up.⁵⁵

You also should consider having an authorized maintenance person from the manufacturer of the tape backup drive or from a third-party repair firm check the alignment of the drive every 12 to 18 months. Most businesses just send the drive back to the manufacturer when it begins to have problems, but if a drive has problems, so can the backup tapes.²⁴

Companies can backup stored tape data across low-cost and readily available IP connections, using both newer native Fibre Channel tape drives as well as older SCSI drives. In addition, open systems servers such as UNIX and NT can be incorporated into remote tape strategies.⁵⁶

VXA is a revolutionary tape backup technology that uses digital packets to store data rather than traditional, linear-based methods. VXA's zero tolerance for error makes it very appealing to IT professionals who demand reliable tape backups. VXA technology offers fast, reliable computer tape backup options for companies of all sizes.⁵⁵

Computer tape backup has become the industry standard for backing up data in most companies around the world. Tape backup offers several advantages over other backup options. One of the advantages of tape backup is the ability to easily store the backup tapes off site, in a secure location. This protects the data from harm that could occur if some kind of natural disaster strikes. It also protects against fire, theft, or any other potential harm that could occur if the data were simply stored on site.⁵⁵

Email has become the number one method of business communication, exceeding even the telephone in importance within an organization. It is a key application in corporate data centers and email servers contain an increasing percentage of corporate data assets. As a result, email has become the mission critical application for enterprises. With this growth in importance comes an increasingly daunting challenge for IT administrators--ensuring that in the event of errors or failures, email can be recovered and restored as soon as possible.⁶⁶

Businesses are now open for longer hours and support a global community of customers which drives requirements for round-the-clock operation. The two backup options are available including hot and cold backups. Cold backup relates to the scenario where application data is tied up for the duration of the backup. However, a hot backup relates to the scenario where a system is performing the backup while applications are updating data.⁵⁹

Current implementations of backup processes are manual, labor intensive, and inundated with problems caused by human errors. Backups that failcan often go undetected leading to potential data loss following a failure. Tapes must be manually inserted, rotated, and removed for off-site transportation to ensure recoverability. Due to the high expenses associated with manual administration, a case for automation can be made where robots are used to improve tape management. Centralized backups group tapes together by pools whereby a number of backups can be multiplexed onto a tape. As a tape is filled the backup continues using another free tape within the pool which significantly enhances manageability. A reduction in the number of tape drives to be managed leads to cost reductions.⁵⁹

For the home system owner nervous about tape backup and put off by having to install the SCSI connector that tape systems need to operate, the Rev plugs into a USB 2.0 port or can connect internally as a standard ATAPI hard drive. Once connected to the host computer, it appears as a regular drive with a letter designation, just as CD and floppy drives do. For businesses looking to back up servers, SCSI and S-ATA Rev drives are planned.⁶⁰

With the odd/even system, you use one tape on one day, a second tape the next day, reuse the first tape on day three, and so on. With the five-day rotation system, you use a different tape for each day of the week.⁴⁷

Make sure you have more than one copy of a backup tape. Instead of using the same tape time after time, use multiple tapes, rotating through them.⁴⁷

Periodically test the backup tapes and restore procedures. You can, for instance, restore the data on them to a different server or to a different partition or folder on the same server where the original information is stored.³

One last thing worth mentioning is your constantly shrinking window for backup. Each day your servers contain more data than the day before. But so many companies are turning into 24/7 operations that administrators are often being asked to back up huge amounts of data during a tiny window of time each night.¹⁰

In the case of tape backup, label the tapes A-H and use the same order to rotate tapes through a tape drive, each day putting a complete backup on the tape. The Towers of Hanoi backup strategy is often used because it creates the longest possible data retention period (the length of time archived data is kept around) with the minimum number of tapes. For example, using the Towers of Hanoi backup strategy with a set of 10 tapes allows for retrieval of data up to 1023 days old.⁶²

The fastest – and most expensive – backup option. If a primary system fails, a fail-over automatically switches to a standby database, server, or network. A fail-over site redirects requests from the failed system to the backup system. Websites are big users of fail-over.⁴¹

This flag requires the -f device flag. This flag causes lssavevg to display information such as volume group, date and time backup was made, uname output from backed up system, oslevel, recommended maintenance or technology level, backup size in megabytes, and backup shrink size in megabytes. The shrink size is the size of the data on all filesystems. The full size is the total size of each filesystem (unused + data). The -l flag also displays the logical volume and filesystem information of the backed up volume group, equivalent to running "lsvg -l vgname".²¹

Verifies the physical block size of the tape backup, as specified by the -b block flag. You may need to alter the block size if necessary to read the backup. The -a flag is valid only when a tape backup is used.²¹

If the filesystem is from a machine named netapp (the number is unimportant and just distinguishes between multiple NetApp machines), then disk backups are available. If the filesystem is not from a netapp, only offsite backup is available.⁵

This flag will display the past 256 backups (roughly). The log is in alog format and is kept in /var/adm/ras/vgbackuplog. Each line of the log is a semicolon-separated list of the file or device name, the command used to make backup, date, shrink size, full size of the backup, and recommended maintenance or technology level (if any).²¹

Analysts also advise that other types of information be available within hours of a manmade or natural disaster. The most cost effective way to meet both needs is to use the same network infrastructure and remote facilities for both synchronous disk backup (for business information essential to continuous operations) and for asynchronous tape backup (for less time-critical but still important data).⁵⁶

Specifies the number of 512-byte blocks to read in a single input operation, as defined by the blocks parameter. If the blocks parameter is not specified, the number of blocks read will default to 100.²¹

Tape Backup (part 2)

Sure, the initial backup can take quite a while to complete and it consumes as much disk space as you would expect it to. But as files that have been previously backed up are modified, the file is not re-copied to the DPM server; only the bytes in the file that have changed since the last backup are copied. This saves disk space on the DPM server and network bandwidth as well.¹⁰

The backup server may back up files on the mirrored servers every day, every hour, or at other defined intervals. Files on the backup server move to offline optical disk storage and eventually to tape storage, which is carried offsite. In the event that corrupted information is written to the mirrored servers, users can fall back to the backup server. If corrupted files are not detected and are written to the backup server, the most recent good file can be obtained from the optical disk or tape archives. This system can be totally automated and run continuously so that the most recent uncorrupted copy of a file can be traced back through the backup server to the archive, as necessary.⁴⁶

To recover, you might need to go to the most recent offline backup set.⁴⁶

The Real-Time Backup Edition contains everything you need to maintain a real-time backup of your mission-critical data. It includes a DataExchange license for two Pervasive PSQL database engines (for the primary and the backup) as well as a one-user count database license (for the backup). The DataExchange engines are restricted to one-way replication, and the replication network is restricted to two databases.⁵²

When you deploy DPM, you designate which volumes or shares on your network should be protected. At that time, Data Protection Manager makes a full backup of all of the files in the protected share or volume. In fact, you can even configure DPM to run backups hourly.¹⁰

If you have more than one local hard disk, copying your data to the other disk provides a certain amount of security. This protects you from a disk failure or and accidental erasure, but leaves you vulnerable if the computer itself is lost, stolen or badly damaged.⁸⁹

Network data mirroring duplicates the full or partial contents of a disk from one system to a disk on another system by sending data over a local- or wide-area network as the data changes. Comprehensive network data mirroring products, such as Qualix DataStar and Octopus DataStar from the Qualix Group, mirror user files, application files and database information for UNIX and Windows NT servers, respectively. Updates to all databases and files are copied as they are output to the source system disk, regardless of whether or not the files are open and in use on client machines. By continuously mirroring data to target systems at remote sites, network data mirroring accomplishes three important objectives.⁴⁴

Designate only trusted people as backup operators, and make sure their rights are limited to only those files and directories they need to back up. As an added precaution, you should make sure that an auditing system tracks and logs all activities of the backup operator.⁴⁶

Now, let's go back to the bigwig who deleted that file he needed for that afternoon's meeting. If Microsoft System Center Data Protection Manager runs hourly backups, the file will have been backed up -- even though it was only created recently. Not only that, there is even a user interface that allows users to perform their own restores without having to call you, the admin! Since the backup is disk-based, you don't even have to load a tape.¹⁰

If you want to back up an entire drive or drives, click to select the check boxes next to the drives you want to back up. If you want to back up specific files or folders on a drive, double-click the drive to expand it. Then continue to expand folders until the files or folders you want to back up are displayed. Next, click to select the check box next to each file and folder you want to back up. If you then want to select files on another drive, click Drives on the Window menu, and then expand the drive and click to select the check box next to each file and folder you want to back up. When you have finished selecting files and folders to be backed up, click Backup.¹⁹

Windows NT Backup backs up the selected data. When the backup is complete, click OK in the Backup Status dialog box. Quit Windows NT Backup to complete the process of making a backup on your Windows NT 4.0-based computer.¹⁹

In the Description box, type a description of the backup. Select the backup type you want to use, and then select the backup options you want to use for this backup.¹⁹

To access a snapshot, go to the directory where the file or directory you need to restore is (or was). Then change to the .snapshot directory. This directory is a special directory which is hidden most of the time. It will not show up when you run ls, but it IS there.⁵

To actually restore the files, change directory to the appropriate snapshot and then copy the file back to it's original location (or to an alternate location if desired) using standard unix commands.⁵

Magnetic tape is the workhorse of short-term backup. The media is relatively inexpensive, so it is reasonable to preform frequent indiscriminate backup of entire servers. The tape backup is a crucial first line of defense against a total disk failure, since the entire volume can be restored at once. Since data is accessed sequentially, it can take a considerable amount of time just to locate the file. The downside is that tape is not as reliable as other media and it has a considerably shorter shelf life, making it inappropriate for archival storage.⁸⁹

The traditional tape backup takes time, money and resources to schedule and manage backups, change disks and tapes, and transport them to a secure facility. To ensure your data is actually restorable, you must test all of your backup media to verify that they are labeled and cataloged properly, un-corrupted and free from physical damage. Most businesses that do their own tape backup, know that data restoration from tape is not reliable.⁷⁹

You never really realize how much is lost until you fire up that key program and it does not work the way it used to. Worse you may have lost that key program and its files.⁹²

If you run a small business, chances are you're saving important files to a server.But what happens when disaster strikes? Many people fail to realize that the loss of files could cripple their business. You can insure your office and equipment, but you can't insure files. Ipso facto, they are lost!⁹⁷

Another problem with traditional backups: In most cases, files that are open are not backed up. Shadow copy has made it possible to back up open files, but many backup applications, especially older ones, do not take advantage of shadow copy. But since DPM is fully shadow-copy-compliant, it can back up files whether they are open or not.¹⁰

Real-time backups take place at any time and must have a procedure for handling files that are open during backup.⁴⁶

Shah used data points showing that tape backups were becoming too time-intensive as data stores grew, plus an explanation that the company's distributed environment required separate tape drives for various systems, to convince the CEO to authorize a move to IBM's Tivoli Storage Manager (TSM) in 2003. Today, Mouser uses TSM to back up a multitude of applications and data, including IBM's UniVerse relational database management system, which houses the company's order entry and financial data, as well as its warehouse control system, graphics servers and file servers.⁴²

Automated backup systems include dedicated backup servers that automatically back up data to magnetic disk, jukebox tape libraries, and jukebox optical disk systems. They may provide hierarchical storage management functions as well. A typical automated system will run 24 hours a day and provide backup services for a number of clients (clients in this case are file and application servers that use the backup services). It provides centralized backup administration, data compression, security, and a number of other features specific to the clients it supports. The Arback and Boole & Babbage products also support remote vaulting. A list of vendors that make backup products is presented on the related entries page.⁴⁶

If a large number of mailboxes are active it is easy to confuse mailboxes and delete one by mistake. The Exchange Backup API supports full Exchange database backup only and does not support mailbox restore; therefore, some interesting methods have been developed to recover a lost mailbox.⁶⁶

Read this white paper if you are responsible for developing a disaster recovery plan for your higher education campus or computer lab. The paper provides information about how to efficiently use tape backup technology in a world rich with Apple workstations and servers.⁹

As always, it is important to choose an option that suits your business and financial situation, but it is imperative that your business has an effective and efficient data recovery plan that covers all possible situations. Offsite storage should be part of that recovery plan.⁷¹

New factors and increased focus in BC/DR planning: BC/DR strategies are affected by the increasing amount of business data being pushed into the mission-critical category, requiring continuous availability. Businesses are also aware that the dangers to their mission-critical data are greater than ever before. Not so long ago businesses had to plan for human error, technical glitches and, of course, natural disasters. Post 9/11, businesses must also plan for terrorist attacks that, as a November 2002 report from Illuminata put it, could "take out more than just a couple of floors of one data center."⁵⁶

Many companies are already backing up their main and branch office systems to tape, but what they don't understand is just how vulnerable their data and their business remains. This whitepaper explores the high cost, complexity and potentially dangerous shortcomings of a strategy based only on tape backup.⁹

CBL and other companies like it want your business, and they try to be helpful in multiple ways. Here's how you can minimize the chances of a tape backup failing in the first place, according to Doug Owens, managing director of CBL's San Diego laboratory and resident tape expert. Many of these same precautions apply to other backup systems as well.⁴⁷

Picture this: The air conditioners in your office malfunction over the weekend and your business servers overheat. Eventually, a fire starts and your computers, drives, and tape backup that were stored in the same location are unsalvageable due to the extreme heat, even by professional recovery services. Irreplaceable data is lost and there is nothing that can be done to retrieve it. An event such as this is completely unforeseen, but its consequence - data loss, is very much preventable. The solution is offsite data storage.⁷¹

A surprising majority of small businesses do not have a reliable backup system. Whether it be due to budget constraints of implementing an in-house backup server or just being unsure of how to implement backups to avoid disaster, many business owners don't realize that they are placing their own livelihood in jeopardy every day by not having a secure backup system. Unfortunately, some learn the hard way and only after a disaster understand the importance of safeguarding their business data. Why wait for disaster and pay thousands of dollars for an attempt to recover the data from a failed hard disk when you can protect yourself for as little as a dollar a day?⁸²

Enhanced Windows Backup uses Windows' built in backup engine called Windows Backup (ntbackup.exe) which provides state-of-the-art core backup technology. Enhanced Windows Backup substantially extends the capabilities of NTBackup, providing an effective integrated backup solution that can take on leading edge but expensive solutions like Backup Exec and Retrospect from companies like Veritas, Symantec and Dantz.⁴³

An integrated LAN attach storage device can provide a complete solution without any IT expertise or advanced knowledge. The HP StorageWorks Media Vault Pro mv2040 is an ideal solution for small businesses, because it combines data protection with simple file serving and secure offsite storage for a total answer to the problem of backup and recovery.³²

But why would you want to back up your system to tape anyway? It's true that only a few years ago hard disk storage cost ten or even twenty times the price of tape drive cartridges for comparable amounts of storage. But now you can buy a 750 MB SATA drive for around $300, and that means tape is now only about half the cost of disk storage.⁶⁴

There are two sizes of Zip disk available, 100 MB and 250 MB. A Zip drive that supports the 250 MB disk size will also support disks of the 100 MB size; 100 MB Zip drives support only 100 MB disks. While the 100 MB disks and Zip drives cost less, you should consider the possibility that some day your data may not fit on a 100 MB Zip disk.⁷³

The lowest level of disaster is a server crash of some sort. This has a very high likelihood of happening some time within a 5-10 year period. It can be either physical (the server dies) or inflicted from the outside, by a virus or disgruntled employee. Your goal in this case is to recover your data rapidly. The most common protection is a tape backup. However, there are several caveats you need to be aware of.⁷⁴

Disasters that affect entire sites or regions � including earthquakes, floods, hurricanes or extended power outages � can render traditional backup technologies useless, even if fault-tolerant devices are employed. Any disaster event that reaches beyond the single building level threatens to destroy not only the primary, operational system, but also the redundant hardware and its backup data. By maintaining a copy of mission-critical data on a target server geographically removed from the source server, network data mirroring eliminates the risk that a site- or region-wide disaster will damage both original and backup data and systems.⁴⁴

Did you get the implication about DVD's? One DVD-R/RW may be able to backup everything on your hard drive. DVD-RW's could be marked for each day week (Monday, Tuesday and so forth) and rotated.⁹²

Tape backup is also a nice option for backup because you are able to backup as much data as you choose without having to purchase additional hardware. All that is required is the purchase of additional tape cartridges to backup more and more data. If you were to back up your data on secondary hard drives, you would have to continually purchase new hard drives as the size of your data grows. Also, hard drives are subject to hardware failures that could render the data unrecoverable. Tape backup is a good option because with it, you're not reliant on any single piece of hardware. The data is stored on a backup tape that can be used in a different tape drive if necessary to restore your data.⁵⁵

Fibre Channel SANs encompass the connection between storage and servers, as seen in Figure1. SANs service a limited number of servers that distribute data to a large number of users over an Internet Protocol (IP) network such as Ethernet. The close-knit Fibre Channel network, known as a fabric, is optimized for large data transfers with low overhead, low-latency switching, and minimal interruptions to the flow of data. A typical user would not have a direct connection to the SAN but would access the data stored in the SAN via a server on the IP network. Fibre Channel increases the performance of data transfers to levels that are unmatched by any other technology.⁸⁷

⁸⁷

Data can be moved from one storage device to another to optimize configurations. As Figure3 shows, reconfiguring data can free up entire storage devices for other applications. Storage in SANs is independent of servers, so it can be logically consolidated yet remain physically separated.⁸⁷