Interview

Data backup and recovery client concerns

SearchStorageChannel.com editors
What are the guidelines for reusing backup tapes? How many times can I reuse a tape?
This is a highly disputed question. Let's start with the fact that tape vendors advertise numbers like 30,000 passes before a tape should be discarded. One use per week might sound like it translates into 576 years (30,000 passes divided by 52 weeks). However, a pass is not the same as a use. A pass is the movement of a given section of media across a section of media. If you are sending less data to the drive than it wants (e.g., sending 20 MBps to an 80 MBps drive), then you're shoeshining. The more you shoeshine, the more you move the same part of media across the media multiple times. If you could figure out how many times you're shoeshining a given section of media, you could divide 30,000 by that number and have your answer. Unfortunately, you'll never get that number, so it's really up to you.

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"real life" of your media in the continuation of this expert response. Why are many companies abandoning tape for long-term archival backups?
Additional Client Concerns
Check out the first installment in our series:
Server virtualization
Most customers are not yet abandoning tape for long-term archival backups. Most are only doing so for short-term, cyclical backups that are stored for month, not years. However, that isn't to say that's it's not a defensible idea. First, they're not (yet) talking about powering them off and putting them on a shelf. However, there are vendors (such as Copan) who are using massive array of independent disk (MAID), where disks are powered off more than they're powered on. In a Copan array, only 20% of the drives are powered on at any one time. The other 80% sleep to save power and cooling.

Get more information on the the future of tape for archival backups in the continuation of this expert response. How can you actually make a snapshot of a LUN on a SAN, and then back it up? Who or what hosts the snapshot, and how is it backed up?
Like many SAN and storage questions, the answer is: It depends. It depends on the software, the storage hardware, the SAN and the implementation. It depends on where the snapshot software sits (in the server, in an appliance, in an intelligent switch, in a storage virtualization device or in a target storage device.) It depends on whether the snapshot is a full volume snapshot, incremental snapshot, read-only snapshot, read/write snapshot, clone snapshot or consistency group snapshot. It depends on whether you are backing up that snapshot to disk or tape and if the backup is local or remote. It depends on whether the backup software is backing the snapshot copy through the server, or if the target storage is replicating the snapshot as a backup to another target storage device. As you can see, there is no simple stock answer to your question without significant qualification.

Click for an example of how to make such a snapshot using Microsoft Storage Server 2003 and Volume Shadow Copy Services of VSS. I am redesigning a network using Intel blade servers with a SAN for clustering in a Windows environment. What are best practices for data backup? Is it possible to install dedicated drives on the SAN for VTL backup?
Depending on the number of servers, the least expensive (and incidentally a very good practice for backup) is Microsoft's Data Protection Server (disk-to-disk backup.) Others that are very good and reasonably priced with the additional functionality of CDP (continuous data protection) are Storactive, Asempra, Asigra and SonicWall/LassoLogic. CDP is incredibly useful today for Exchange data protection.

Get methods for selecting backup technologies for SMBs. We are planning to change our backup strategy from tape to NAS. What are my options?
Using disk storage, in this case NAS, as a backup target has been very popular with the reduction in disk costs and the realization that recovery time has significant value. In a NAS backup architecture, the disk resides behind a filer head that shares file systems via NFS or CIFS, and backups are sent to those file systems. NAS filers are typically easier to maintain than traditional disk arrays. When choosing backup software, it is important to remember that you need software that supports NDMP when using NAS as a backup target.

Get more information on NAS channel issues. I'm having problems backing up files larger than 1 GB to a tape drive. What might the problem be?
There are known file size limitations with older versions of Windows (i.e. 2 GB with FAT). However, a 1 GB limit is well below that known limitation that very few people run into now days. It might be a good idea to look at the tape device configuration parameters. Depending on the tape device utilities installed, it might be possible to look at and change configuration parameters like block size, maximum number of blocks and end of tape marker. An erroneous maximum number of blocks or end-of-tape configuration could very well limit the amount of data that can be written to tapes mounted in a particular device.

Get an indepth guide to helping customers handle backup projects. How far away should backup tapes be stored offsite? How is this distance was agreed upon?
There might be some industry specific guidelines to assist with the decision (the banking industry comes to mind) but no standard or minimum distance has been established. There is typically much more documentation about "how" tapes are stored rather than how far. There are obvious bad choices such as keeping backup media on a different floor of the same building or even in a neighboring building. That said, it might be acceptable in a particular area to have backup tapes stored in a vault a few city blocks away from the data center. In other areas, such as hurricane-prone regions, the tapes must be kept at a distance greater than the destructive reach of the weather phenomenon.

Get more information on disaster recovery channel issues. A laptop shut down with a USB stick in the USB port because the battery was low. After restarting the computer, XP reported "USB device malfunction and device not recognized." Reinstalling the driver didn't help. Is there a way to retrieve the data?
Unfortunately, this type of storage device stores data on memory chips rather than on magnetic media such as a hard drive or tape. This can present some challenges when it comes to recovering from data loss or corruption. Data is typically not "erased" from magnetic storage media unless it was purposely cleansed using a specialized utility; this makes it retrievable using software products or a data recovery service provider. However, when it comes to solid state media (memory chips), data could potentially be "flushed" from memory. Not to say that this is necessarily the issue with your particular device, but you probably should consult the vendor's support center to determine what your options are.

Get more information on this USB data recovery issue in the continuation of this expert response. What is the best alternative to having tapes physically collected and stored offsite?
The best practice is to replicate backups to a remotely located backup device or service on a regular basis. This reduces the risk in catastrophic disasters where the entire building is lost. Short of that, regularly collecting tapes and shipping them offsite to a fireproof, temperature controlled location is also good.

What happens when users are working during a SQL Server 2000 backup?
When SQL Server does an online hot backup, users can continue normal transaction activity. During the backup operation, updates are logged within SQL Server's transaction log. Reduced database performance is the most likely issue when backing up SQL Server while the database is online and being used actively. The degree of impact will depend on the power of your server hardware (CPU, memory, etc), speed of your backup infrastructure and the volume of transactions hitting the database. If you have a very busy SQL Server, you will have to ensure that your infrastructure is tailored to handle the high volume of transactions while it is also being backed up in order to provide response times that are up to your users' expectations.

Get more information on SQL Server channel issues.


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