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Choosing the Right tape drive

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PCQ Bureau
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Let's face it. There's no replacing tape for backup. At least not yet. Tapes have perhaps been the longest running storage devices, and are still going strong. While quick and dirty solutions like DVDs or CD-Writers are also available for back up, there's no replacing tape when it comes to large volume back ups and archives. Their throughputs and capacities are on the rise, price points have come down and new technologies are evolving everyday. Today, there's a variety of options to choose from in tape drives-starting from single cartridge tape drives and autoloaders that can take multiple cartridges to tape libraries for very large volume backups. Add to that the fact that they're available in different technologies (DAT, DLT, LTO, etc), interfaces (IDE and SCSI), and even as external or internal devices. So, which back up device do you choose?

Which Tape Technology?



Tape technology decides both the throughputs and capacity that you can get and the overall running cost
Choosing the Right tape drive



While DVDs and CD-Writers are quick solutions for back up, there's no replacing tape when it comes to large volume back up and archives
How we tested



We used a three-axis model of performance, price and features to arrive at the results and the Brown Gibson model to arrive at the winners
Sony SDX-520C/R AIT-2
HP DAT 72
Sony

SDX-400C/R AIT-1
Sony

AITe-90-UL AIT-1
Tandberg

VS-80 DLT-IV
Sony SDT-11000 DDS-4
Sony SDT-9000 DDS-3
Sony SDX-700C/R AIT-3
HP 460 LTO-Ultrium 2
IBM LTO-Ultrium 2

When going for a backup solution, the choice is not purely based on technology alone. It starts with defining your business requirement. How much data do you really want to backup? The most common answer to this question is “all of it”.

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Unfortunately, the cost associated with this could be enormous. Imagine if you have 200 nodes on your network with 30 GB hard drives on each. It's unlikely that all of it would be important data to back up. Even if we assume 50% of it is important, then we're talking about 15GB x 200 or 3000 GB of data to be backed up! The cost to back up this itself could be prohibitive. Now imagine having to also pay for the other 50%, which doesn't really need back up. Therefore, it's important to first identify how much of your total data is critical to your business, without which your business could really suffer? Chances are you'll get a totally different picture.

Tape applications



After deciding how much data to back up, other questions come up. How frequently do you need to back up the data? What's the purpose of back up? Is it for archival or is it for live storage? It's important to, therefore, understand what kind of applications can tape storage be used for. While a tape is mostly associated with backup, it's also widely used for disaster recovery and archiving purposes and can also be used for data distribution and hierarchical data management. Let us briefly describe the differences between these various usages of a tape.

Backup is making copies of files originally stored on hard disks and is required to restore lost or damaged files. Backup files are redundant copies and are not used as working copies. Backup files usually have a limited life and are overwritten by newer files depending on the backup policy in place. A typical example is backing up a file server, with a weekly cycle where the tape data is overwritten every week with new data.

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Archiving is copying files on tapes for long-term storage and the files may not be a copy of some original but could be the original itself. Archival data has a longer life cycle than backup data and the chances are that it may be kept safe for the entire life. Examples of archival storage are digital music or image museums, where data has to be permanently stored even for the next generation. Another could be legal reasons, where documents have to be maintained for, say, at least 5-10 years.

Archival, therefore, is not purely a business imperative, but is also driven by legal regulations. For instance, the time period an ISV store e-mail logs or a bank store records are all driven by legal regulations.

Disaster recovery involves recovering from a situation where the whole system or multiple systems are knocked out. Disaster recovery requires more hardware and software features than any other application. First, the entire system state with its configurations and data are backed up on a tape. The backup software also writes additional information for restoring the system to its exact original state. Next is hardware, which is the tape drive. Some tape drives let you boot the system from the tape itself, after which the entire system is restored back to the disk from the tape. Other options could be booting off a floppy or CD-ROM and then recovering the system from the tape.

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Since there are so many applications for tape, you need to put in a proper strategy to guard against data loss due to disk crash, human error, viruses, theft, and natural disaster. Also, since data backup and recovery is a time consuming task, it requires careful planning and implementation. Some important issues here include choosing the right backup drive and media, and whether to go for feature rich yet expensive commercial software, or the default one that ships with your operating system. Installation also comes with its own share of problems. Interface and driver issues become a major problem for many and should be a main criterion while purchasing hardware.

After your hardware and software is in place, defining the backup scheme and implementing it on a regular basis becomes critical. Daily maintenance chores like tape drive head cleaning, rotation and replacement of tape media should be strictly followed as defined in the policy to make backup and recovery an easy task.

So, as can be seen, defining the right backup infrastructure is not an easy job. But, careful planning and identifying your business requirements can help you choose the best options. Plus, in the pages to follow, we have covered various single-tape backup devices available in the market. We tested them for performance in backing up and restoring data, features that make them easy to use, capacity, price, and the technology they used. The drives range from handling small 12-50 GB backups up to 400 GB.

Anoop Mangla

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