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This document discusses the issues involved in setting up an effective backup strategy to prevent data loss on individual or networked computers. It first shows the value of your data and how it can be lost. Then it explains the distributed and centralized approaches to backing up networks. This white paper details the general hardware and software features necessary for a successful backup solution, then discusses the administration costs of implementing and maintaining the solution. It goes into more details about hardware features, benefi ts, and costs. Finally, it offers several software options for your consideration.
The majority of organizations today fail to adequately protect their corporate data. Organizations around the world are storing vital data on personal computers—mainframes and minicomputers are no longer the sole repositories of the accumulated corporate knowledge. Despite this shift, most organizations still operate without a functional backup strategy to ensure the integrity of their criti- cal, decentralized data.
Sporadic investments in earlier generations of backup software and hardware for personal comput- ers have proven ineffective, mainly because they are cumbersome and go unused. However, the latest generation of personal computer backup and restore software, together with high capacity media and high speed storage devices, provides unobtrusive, reliable “electronic insurance” of a quality previously found only in mini- and mainframe computer.
Users who have implemented an organization-wide backup strategy have identifi ed four major benefits:
Significant cost savings
As users store more and more information on personal computers, the value of the data soon exceeds the value of the hardware. In fact, the average personal computer used in business costs a fraction of what it would cost to recreate the data stored on the computer.
When a computer or mass storage device fails, its user needs to be able to resume work immed- iately. Without backup, the user spends hours, days, even weeks rebuilding the hard disk and re-creating lost documents. As the user’s productivity diminishes, so does the productivity of the user’s organization. A dependable backup system protects information and maintains productivity.
Simplicity for end users
Users questioned about backup invariably respond that they know they should back up but tend not to because it is “too much trouble.” Yet the technology exists today to remove that burden by using network-aware backup applications that centralize the backup of entire networks of personal computers.
A more secure computing foundation
As more and more tasks, such as productivity, presentation, and communication, are performed on desktop computers, a sound strategy of regular backup becomes essential. Without a solid foun- dation for computing, greater dependence on desktop computers results in greater vulnerability.
Until you actually experience some sort of data loss, you may not realize to what extent loss is possible and the ultimate effects the loss may have. Consider documents, for example. Because of the gradual nature of their creation, most users are not aware of the value of their total investment in electronic documents until they lose them. And documents aren’t the only form of data you can lose—consider all of the components of your complex computing environment that you can lose as well:
Modern computer operating systems are complex, with many files in many folders. You probably have an impressive collection of third-party drivers, fonts, control panels, and other system-related resources, which would be tedious to reassemble after a disaster. Your ability to restore that precise system environment is a critical component of any backup strategy.
Re-installation from disks, CDs, and the Internet is tedious at best and disastrous at worst.
Applications allow signifi cant customizing during and after installation. You invest in a set of choices; gradually creating the confi guration that works best. For example, a spreadsheet application may al- low you to customize menus and tool palettes, and even automate data exchange with other appli- cations. Should disaster strike, this customizing might be diffi cult and time-consuming to re-create.
Users are well aware of the complex and fragile nature of any network environment. This is an area where various hardware and software components interact with other original equipment and third-party products. Users whose network environments have evolved over time fi nd they have dozens of interrelated software modules: libraries, control panels, data fi les, and even applications. An incompatible version of one of these fi les often results in network failure. Therefore, complete restoration of the network software environment has to be part of any backup strategy.
Data stored on computer is always in danger of being destroyed. All kinds of businesses—from the very large to the very small—lose critical data every day, usually for one of the following reasons:
Most data loss occurs when users inadvertently delete files, folders, or even entire hard disks. Such “unintentional computing” may result from “mistaken identity” of data, disorganized hard disks, or inadequate training. Estimates suggest the vast majority of all lost data is accidentally deleted by users.
Hard Disk Failure
Because hard disk drives rely on precision tolerances, spinning disks, and floating magnetic heads, failure is a given. It is only a question of when a drive will fail, not if. With almost every personal computer employing a hard disk as its primary storage device, literally years of work may be stored there. Without backup, all of this data can be lost.
As a result of all the media attention, most users are now aware of the dangers of computer viruses. These renegade programs can “propagate” themselves from computer to computer, sometimes remaining benign but all too often destroying fi les or even reformatting hard disks.
Personal computers are a favorite of thieves of high-tech equipment. Many organizations have lost almost every computer they own in a single night. Along with the hardware goes the data, which is often even more valuable.
The relatively unlikely occurrence of a fire, flood, or earthquake is offset by the catastrophic loss such a disaster would inevitably bring.
Developing a Backup Strategy
Perhaps the most important consideration in developing a backup strategy for desktop computers is deciding whether to employ a distributed or a centralized strategy. For many organizations the default backup strategy is distributed, allowing the few users particularly concerned with data integrity to perform sporadic backups on their own. Many users and network administrators alike may not be familiar with the entire range of backup alternatives.
You may want to keep the responsibility for backup in the hands of the person generating the data: the individual user. Users are often the fi rst to appreciate the importance of the data they individu- ally create, so they have a built-in incentive to back up that data. In addition, you don’t have to designate individuals with backup responsibility for others.
A distributed strategy may work best for users such as graphic designers, who want to store data as both backups and repositories for large, infrequently accessed files they can retrieve at will. A distributed strategy may also be the only choice for users isolated in a satellite office or home office.
The key to success in implementing a distributed strategy is setting standards and following a consistent program of user education and training. The biggest single disadvantage of a distributed strategy is that individual users are notorious for avoiding backup. It is very diffi cult to achieve a mandated level of “data insurance” by relying on a user’s initiative. Also, when a large number of users require a backup solution, buying separate storage devices becomes very expensive, and carting around storage devices from place to place is often impractical.
Local area networks (LANs) can centralize the management of backups. There are two types of cen- tralized strategies.
The desire to centralize backup administration and simplify the backup task for workgroups has resulted in many organizations deciding to back up only servers. Users are encouraged or even required to store important fi les on the server. While this strategy does centralize the administra- tion of backup on the network, it lacks complete data protection because users disregard regular backups. However, when centralized backup is implemented in phases, server backup is a good fi rst step toward a comprehensive system.
This strategy encompasses the backup needs of both servers and desktop computers. It is more reliable because responsibility for all administration tasks is removed from the user. It is more complete because all of the user’s data is backed up, not just selected fi les. This strategy requires little additional cost. Typically, all the data is collected and managed by a backup application running on a central computer with a high-capacity removable media device. While the central computer is often a file server with the backup application running in the background, it can just as easily be any computer on the network.
The comprehensive strategy has the following advantages:
The single largest disadvantage to a centralized comprehensive backup strategy is the organization must designate individuals responsible for backup administration. Though the current generation of tools makes this task relatively easy, the backup administrator must be willing to accept the respon- sibility. Fortunately, most organizations already employ people who provide this kind of service.
Evaluating Solutions and Requirements
The basic idea of backing up is simple: make extra copies of important fi les and put them in a safe place. However, determining the requirements of your backup strategy involves making decisions about such matters as performance, unattended operation, security, storage, and hardware. Much of the functionality of a backup system is determined by its software, so that is a logical place to start evaluating features.
Backups must be reliable to be effective. An unreliable backup is rarely better than none at all. Reli-ability typically concerns three areas: verification, reduction of user errors, and backup strategy.
There are many types and degrees of verifi cation. First and foremost, the verifi cation procedure should check each area of potential data loss. The highest level of security comes from a “double read back” verify. Once the backup operation is complete, all copied data is re-read from the source and compared byte for byte with the data on the backup media. Although this method incurs a performance penalty, it verifi es that data was read correctly from the source, was transmitted via the storage device to the media without error, and maybe read again from the media.
Reduction of User Errors
Features designed to prevent common user errors radically increase reliability. Backup software should be easy to install, use, and understand. Otherwise, backups may be unintentionally incomplete. Backup software should request tapes by name and check each tape’s name before writing to protect valuable data from being overwritten. The software should also record the precise state of documents as well as user and network environments to facilitate fast restores should disaster strike.
Reliability is greatly influenced by backup procedures. The protection provided by the backup solution not only depends on the frequency with which backups are performed, but also on the extent to which the backed-up files are themselves safe from loss or damage. In essence, the specific strategy you implement determines the types of catastrophic events against which your users are insured. This is similar in principle to insuring against eventualities such as fire, flood, and theft.
You can increase the degree of backup protection by adopting the following schemes:
Rotating Among Backup Sets
Backing up to tape, disk, or other media provides a second copy of vital data, but even tapes and disks can be damaged or destroyed. The solution is to rotate among multiple backup sets. For example, back up to the first set today, the second set tomorrow, and the third set the following day, and then back to the first set. This reduces the risk of losing data. The key is to use software that properly handles incremental backups to rotating backup sets.
Off-Site Media Rotation
Multiple backup sets protect against media damage, loss, and failure, but not against natural disasters such as fires, which can destroy all of an organization’s computers as well as the very backup on which the organization depends for recovery. Consequently, backup systems provide the highest degree of reliability by regularly rotating copies of the backup off-site. In combination with a mul- tiple backup set scheme, this creates as fail-safe a scheme of data protection as is possible.
Performance is a key factor to evaluate because backup applications handle much more data than other software. Performance infl uences both capability and level of protection. Capability is affected because the greater the performance, the more you can back up in a given time. The level of protection is affected because the essence of backup is making multiple copies, and higher performance facilitates their creation and timely verification.
More important than the performance of any specifi c component is how the backup application, source drive, destination device, and “data pipe” work together as an entire system. For instance, the maximum throughput of a tape drive may be meaningless to the performance of the overall system if the software and data transmission components cannot consistently deliver suffi cient data to “feed” the tape drive. In this case, a faster tape drive could even decrease the overall performance of the system when “data starvation” causes the storage device to spend more time repositioning than copying data. Backup software should never sacrifi ce reliability for performance.
Full and Incremental Backups
The greatest improvements in performance result from backing up only new or unique data to each backup set. The first time a backup set is used, all desired fi les are copied. This is known as a full backup. Usually, backups subsequent to a full backup are incremental; only fi les created or modified since the last backup are copied. This saves considerable time and backup media space. A common strategy is to do regular incremental backups to save time and space, with periodic full backups to reduce the size of a complete backup set.
Backup administrators often shy away from incremental backups because most backup software does a poor job of restoring from incremental backups. Select backup software that allows you to execute a complete restore of just the most recent fi les from a combination of full and incremental backups in a single pass.
Cache and other temporary files do not need to be backed up because of their temporary or volatile nature. Because these fi les have no value, they should not be backed up. Excluding this and other temporary files from backup can reduce backup requirements significantly.
Compression of data, which can be handled by some backup devices and software, can dramatically reduce the amount of storage media required for a given amount of data.
Many backup devices have compression abilities built in to their hardware so they can quickly compress data “on the fly” during backups. The backup application should recognize the compression ability of the backup device and use hardware compression when it can, but when hardware compression is unavailable; the application itself should compress the data.
Data compression duties can be handled by some backup software. Although software compression may exact a performance penalty, it may be reduced because there is less (more compact) data to store on the media. A fast backup computer and backup software with a fast compression algorithm can make software compression so fast as to be transparent to the user.
Software data compression can be used to compress backups exchanged among computers and backup devices, as the hardware compression facility on a given backup device may not be compat- ible with the facility of another. In addition, software compression is used when saving to encrypted backup sets because encrypted data cannot be compressed effectively.
Performance for Network Backup
Performance is perhaps most important when servers or entire networks are being backed up, because of the sheer volume of data and the limited time in which to back it up. With a centralized strategy, increased performance can mean:
Because a centralized strategy often relies on the network to transport data, managing this part of the “data pipe” efficiently can radically improve performance of the backup.
Fortunately, backup software can use a number of techniques to enlarge the boundaries of network backup and improve performance. The most innovative technique dramatically reduces the amount of data to be transmitted during backup before the backup even begins.
Optimizing Network Transfers
For most network operations, performance is determined more by responsiveness than by data throughput. This priority is reflected in network protocols that use relatively small block sizes and wait on acknowledgment. With backup, however, maximizing data throughput is much more critical than responsiveness. Optimum performance requires pipelined data fl ow with a separate acknowledgment “channel” that may trail the current data block by a significant degree.
Intelligent Data Reduction
Identical files are often found on many computers on a network. Recognizing this redundant information and not recopying it unnecessarily saves both network transmission time and storage requirements. For many networks, intelligent data reduction decreases the data to be transferred during a full backup by one-third, increasing the amount of unique data that can be backed up. Intelligent data reduction’s actual effect depends on the amount of “identical” files on the network and varies with each organization. Data reduction effectively increases both the amount of data that can be backed up and the effective capacity of a backup drive, providing room for growth. The first backup to a new backup set copies all files. Subsequently, identical files are not copied.
Performance for Individual Backup
Even with a distributed backup strategy, performance is often the most important criterion in select- ing a solution. With a distributed strategy, increased performance can:
Deciding how, how often, and which data to back up is similar in principle to deciding on insurance coverage. The frequency of backups largely determines your exposure to data loss; frequent back-ups reduce the amount of data lost should disaster strike. However, like lowering the deductible on insurance, increasing the frequency of backups has its costs: escalating the requirements for backup hardware and the amount of time needed for operation.
Most users realize that not all of their data is of equal value, nor is it modifi ed by users at the same frequency. Users tend to want to back up some categories of fi les more frequently, others less frequently, and some not at all.
For example, it is common to fi nd backup schemes in which documents are backed up most often, applications and system software less frequently. However, powerful features such as incremental backups and “intelligent data reduction” can supersede the need for these types of schemes.
Backing up all files instead of selected categories has signifi cant advantages. When a restore is required, all documents, as well as the system, application, and network environments, can be recovered quickly and easily, usually in one step. Still, some special situations may require selective backup of documents, applications, system software, and so on. Some backup applications have the fl exibility to support these criteria.
For many organizations, security is a primary consideration in evaluating backup solutions. Well-designed backup solutions can provide easy-to-use—yet powerful—options for securing data.
Most backup solutions duplicate an individual’s data on removable media of one form or another. While this is usually the best way to store backup information, the copy may also unwittingly make an individual’s or even an entire organization’s most valuable data very easy to steal. Therefore, many organizations that place a premium on security should select backup products with security features that can be tailored to their requirements.
Security for Individuals
Security can be as simple and as inexpensive as storing the backup set under lock and key. There is a way to ensure that backups remain secure, even if they fall into unauthorized hands. Encryption is a common technique that prevents access to backed-up data by users without the encryption key, or password. From an administrator’s perspective, encryption can be very easy to use, simply requiring the selection of a feature and the entry of a password when a new backup set is initiated.
When the encryption feature is selected, data is processed before being copied to tape or disk to encode it according to the encryption key. As a result, the data on tape is in a code that can only be decoded with the encryption key. The United States government has been one of the leading developers of encryption technology, and its Data Encryption Standard (DES) technique has become the de facto encryption method in the United States. With the rise of the Internet, other encryption methods have emerged as well.
Security for Networks
Centralized backup presents greater security challenges and opportunities. A centralized backup scheme has challenges in the form of more ways for an unauthorized individual to access data. On the other hand, centralization allows you the opportunities to implement a more consistent, unobtrusive, and comprehensive security scheme.
To provide additional layers of security with a centralized scheme, network administrators should protect backup sets under lock and key and/or encrypt the backup set itself. Other potential points of entry should be protected in the following ways.
Centralized network backup solutions depend on the network to deliver data. As a result, there is a risk of unauthorized “wire tapping” by a device that “peeks” at network data traffi c. Therefore, network backup should provide safeguards to protect data on the network. The network administrator can prevent unauthorized wire tapping if the backup software ensures that all data sent from servers and users is encrypted before transmission.
Network Password Access
With the power to reach across the network and copy all of the network’s most important infor- mation, security concerns require that the network backup application have rigorous safeguards. Control of access with passwords is perhaps the most important. The central backup application controls all backup access to other computers in the workgroup, so it should be protected by a password. To prevent users from gaining unauthorized access by using their own copy of the back- up application, the software on the networked computers should likewise require a security code for any access. Along with password access to the application itself, this scheme ensures private, secured communication channels between backup nodes and the central application.
Individual and Organizational Security
In organizations with very rigorous security requirements, highly classifi ed information may have to be strictly confi ned to the users themselves. In these situations a user with highly classifi ed data can still benefi t from the advantages of network backup that allows the exclusion of certain directories or allows the use of other desktop security software. This kind of fl exibility lets organizations tailor the security of their backup solution to their exact requirements.
The repetitive nature of backup makes it perfectly suited for automated operation, relieving the user of a burdensome task. To quickly and easily automate your backup strategy, backup applications must include two critical functions that allow unattended operation: scripting and scheduling.
A script is a saved procedure involving several elements and a few steps, and its purpose is to auto- mate the procedure of a given task. After you defi ne a script, you needn’t make the same repetitive sequence of choices for every backup operation. Scripting must be powerful enough to include all the operations and options you want, yet not so complex that you have to invest inordinate amounts of time setting up the scripts.
Invest in backup software that doesn’t require all backup sources or destinations to be “on-line” at the moment the scripts are created because it is often impossible to ensure all sources, including notebooks, will be available at any given time.
Backing up is most effective and unobtrusive if it is done when the computers and the network are relatively inactive. Typically, the backup administrator is not present at those times, and scripts must be executed automatically. Required scripting features include multi-script execution and automatic repetitive scheduling.
Unattended operation results in dramatically lower administration costs and, in some cases, greater reliability. If you want to perform unattended backups, you need a device that can store an entire period of data on a single device. If you cannot perform a complete backup in this way, backup will be delayed as the software waits for new media. This is a particular problem when backups are scheduled overnight or on weekends when administrators are away from the backup computer.
You can never have too much storage capacity, as it directly translates into less frequent adminis- trator intervention to swap media. With adequate capacity, both full and subsequent incremental backups can be automated, usually requiring no attention until the backup device is completely full.
Whether your strategy is centralized or distributed, administration costs are likely to be a major consideration in evaluating the overall cost of the system. With a distributed strategy, spreading the responsibility for backup among the users hides the true cost of backup administration for the organization. However, in most cases these hidden costs reduce user productivity and decrease the reliability of the backup. Even though a centralized backup strategy requires a central administrator, it usually results in lower overall administrative costs.
In either case, the design of the backup system in g eneral and the backup software in particular can greatly lower administration costs. A backup system designed for unattended operation usually minimizes overall administration costs. In this case, the reliability of the system should be the main consideration. Enhanced reliability helps ensure that backups are uninterrupted by errors and that they occur continuously without the administrator’s attention. Robust network support, error handling, and automated verifi cation can increase overall reliability, reduce requirements for intervention, and minimize costs.
Determining backup storage requirements helps you select the right backup hardware. More storage capacity allows more unattended operations, making administration easier. Therefore, it is often useful to choose a backup device and media which have storage capacity greater than or equal to all the data to store.
To determine minimum backup capacity requirements, simply calculate the total capacity of all the hard disks you want backed up. Selecting a backup device with capacity even greater than the minimum storage requirement brings several benefits:
Because of these benefits and low media cost, tape drives are a good choice for individual or network backups. However, if you want a more flexible device which has other uses in addition to backup, you should consider the multiuse storage devices discussed under “Backup Hardware Options.”
Conceptually, determining the storage requirements for network backup is little different from determining the capacity for individual backup. Simply add up the capacity of all the drives to be backed up on the network, including servers and individual computers.
If unattended operation is important, select a drive with capacity greater than the aggregate capac- ity. Network backup almost always demands a high capacity backup storage device. This tends to narrow your hardware options to tape drives, as discussed in the following section.
This strategy yields benefi ts which are basically the same as those of individual backup. However, there are additional considerations.
You can choose from several networking alternatives to provide an appropriate data pipe for any network backup requirement.
A slow network can be a bottleneck to a network backup system, and a fast network can transfer data as fast as some backup devices. A TCP/IP implementation over Ethernet cabling should be adequate for most installations.
If your backup system includes some implementation of intelligent data reduction, it minimizes the amount of data to be transferred over the network.
An appropriate strategy for multiple zone networks must take into account the possible performance penalty exacted by network routers, which can degrade network throughput. Administrators should carefully construct backup workgroups to avoid crossing routers unless they are modern, high-performance hardware routers.
Dial-In or Remote Networks
Backing up computers over a modem or dial-in network connection is possible but not advisable because of the low throughput of the typical network phone bridge. The speed of your network bridge, the reliability of the connection, and the amount of data you wish to backup determine whether backup over a temporary connection is feasible.
In addition to all the strategic issues discussed so far, also consider the potential growth of your personal computer or network. Larger hard disks will require more backup storage capacity. Back- ing up all the additional data in a limited amount of time may require faster hardware, including the backup computer, backup device, and the network over which the data travels. You never can have too much storage space nor too much speed for backups. It may even be necessary to implement more comprehensive backup strategies to handle future growth.
Backup Hardware Options
Hardware solutions fall into three categories: drives for network or server backup, drives for individu- al backup, and multi-purpose drives for a variety of uses. This section discusses the relative merits of all the options, and compares their advantages and disadvantages.
In evaluating hardware—especially tape drives and particularly compression drives—the rated capacity should usually be viewed as the theoretical maximum. The capacities achieved in day to day use are often significantly less.
The actual amount of data that will fi t on a given medium will vary due to many factors. For instance, a tape’s capacity can be greatly infl uenced by the relative speeds of the backup computer and the tape drive. Another factor is compression, a feature of some drives and software which reduces the size the backup data occupies on the media. Theoretical maximum capacity representations refer to the amount of data before it gets compressed by a tape drive with hardware compression capabil- ity—and they often assume generous compression rates.
When selecting backup hardware, the cost of the necessary media is often overlooked. It’s important to consider the cost of media that will be required to adequately meet the needs of the system.
If you have not calculated media usage requirements for a specific backup system and are just comparing the relative costs associated with various backup hardware, then assume purchasing the media required to build three complete backup sets. That will give you enough to figure out an extended cost for each backup device.
Tape drives are built exclusively for backup functions. These devices store several to many giga- bytes of data per cartridge, and additional media cartridges are relatively inexpensive. Modern tape backup devices offer excellent throughput, making them the number one choice for both server and network backup. Entry- to mid-level tape drives also make good choices for personal backup devices where large quantities of data need to be backed up.
8mm drives offer moderate speed and good capacities for medium-size environments. Capacities range from 2.5 to 40GB with transfer rates from 60 to 80MB/minute.
ADR (Advanced Digital Recording)
ADR drives provide a high speed solution for desktops and single servers. With transfer rates of 30MB to 120MB per minute and capacities up to 50GB, ADR and provides users with a fast, high capacity backup.
AIT (Advanced Intelligent Tape)
AIT is appropriate for environments demanding high capacity and high performance. Each cartridge can hold up to 50GB (more using built-in hardware compression). AIT drives can transfer data up to 360MB/minute.
DAT (Digital Audio Tape)
DAT spans the gap between entry-level tape drives such as Travan and higher-level products such as DLT and AIT. Each compact DAT cartridge, containing 4mm wide tape, holds about 12GB (DDS-3), 20GB (DDS-4), or more depending on how easily your fi les are compressed. Speeds can range from 6MB/minute to 150MB/minute.
DLT (Digital Linear Tape)
DLTs are high end drives with high capacities and fast transfer rates. They use half-inch wide tape cartridges available in sizes ranging from 10 to 110GB (more using built-in hardware compression). DLT achieves transfer rates up to 600MB/minute with a fast computer and large fi les.
LTO (Linear Tape Open)
Linear Tape Open devices are one of the highest capacity, highest speed drives available. Ultrium format drives can store up to 100GB at speeds up to 20MB per second (more using built-in hardware compression).
Mammoth tape drives, based on an 8mm AME (Advanced Metal Evaporative) format, are fast and are an excellent choice for mid- to high-level backup needs. They store 60GB (more with built-in compression) per cartridge and offer transfer rates exceeding 16MB per second.
Travan/QIC (Quarter-Inch Cartridge)
Travan/QIC drives are relatively inexpensive and have a wide range of capacities for small business/ home offi ce environments with average requirements. These drives can hold from 4 to 50GB on each tape and speeds range from 30 to 300MB/minute respectively. Some Travan/QIC drives offer hardware compression, some do not.
VXA drives provide a new tape technology that is reliable and relatively inexpensive for small to medium-sized environments. VXA formats data in packets, operates at variable speed, and can read data multiple times in one single tape pass.With capacities ranging from 20 to 66GB and speeds up to 360MB/minute, the VXA-1 drive gives you a lot of fl exibility at a very cost effective price.
Autoloaders and Tape Libraries
Tape Libraries are ideal for unattended backups, particularly over computer networks, and they al- low for great fl exibility. A tape library consists of a tape drive and robotics that automatically move tapes between a magazine and the drive mechanism. They are available with drives of most every tape format. Their speed and capacity depend on the particular type of drive installed and the num- ber of tape slots available.
Excepting tape drives, most other storage devices can be utilized for purposes other than just data backup and archiving.While these devices vary greatly in their storage cost per gigabyte, their multi- tude of functions make them quite attractive by spreading such costs across several different uses.
CD-R and CD-RW (Compact Disc Recordable and Rewritable)
CD-R and CD-RW drives store data on special compact discs and provide a practical and cost-ef- fective backup solution for modest requirements. CD-R and CD-RW drives store 1.2GB (more with software compression) on each disc. The speed of CD-R and CD-RW drives vary and can range from 5 to 50MB/minute.
DVD-RAM (Writable Digital Versatile Disc)
These writable DVD discs are the newest technology in storage. Each DVD-RAM cartridge can hold 4.7GB on each side for a total of 9.4GB on a double-sided cartridge with speeds up to 60MB/minute.
Hard Disk Drives
The rapid increase in hard disk drive storage capacities and their decrease in price have made them attractive for backup use. It’s important to keep in mind, however, that the nature of the “fi xed” disk drive does not necessarily promote portability and off-site storage, the latter of which is vital to any complete backup strategy. This category may also include Network-Attached Storage (NAS) devices accessible to the backup software.
MO drives provide instant access to large amounts of information and the optical disks are not sus- ceptible to head crashes, stray magnetic fi elds or media wear. MO technology can be rewritten, mak- ing it a good choice for backup and useful as a high-capacity, high performance replacement for 3.5” fl oppy disks. Using both lasers and a magnetic head, MO drives support either 3.5” discs, holding up to 1.3 GB, or 5.25” discs, holding up to 5.2GB. Speeds range from 60 to 120MB/minute.
Removable Cartridge Devices
SuperDisk, Zip, Jaz, and Orb drives are great for personal backups, transferring fi les between com- puters, or storing unneeded fi les. Capacities can range from 100MB to 2.2GB with speeds from 30 to 480MB/minute. Media for these devices, however, can become prohibitively expensive for larger data backup requirements.
Retrospect Server Backup
Retrospect Server Backup includes the Retrospect application plus 100 clients to back up desktops, notebooks, and servers. Servers may run the backups or be backed up as clients across the network. Retrospect Server Backup includes advanced networking features useful for larger networks, such as the ability to back up across routers using subnet broadcast or direct IP addressing. Clients may have static or DHCP-assigned IP addresses. Retrospect Server Backup is available for Windows com- puters and is expandable with the addition of Retrospect Clients.
Retrospect Clients allow Retrospect Desktop,Workgroup, and Server editions to back up other computers over the network. Adding Retrospect Clients to Retrospect provides a centralized backup solution and allows you to use a single computer with a storage device to back up networked computers.With Retrospect, you can schedule your network backups to run unattended during con- venient times such as nights or weekends. Retrospect Clients are available in packs of 5, 10, 50, and 100. All client packs are cross-platform for Windows or Macintosh computers.
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