Monday, December 12, 2011

Transitioning from tape to a disk backup appliance

When an organization discovers just how well disk-based backups overcome the challenges that have long been a part of tape backups, it is tempting to say “out with the old and in with the new.”

However, making the switch from tape backups to a disk-based backup appliance requires a lot more planning than might be expected. You have to account for a number of different factors, including your ability to restore data that was originally backed up to tape.

Lab test your new backup solution
When you purchase a disk backup appliance, the first thing that I recommend is to test it in a lab environment. It may be tempting to connect the new backup solution to your production network and immediately begin using it for backups, but doing so can cause problems.

The reliability of using a new backup appliance to back up a production network should be a main concern. If the backup does not work in the way that you expected (which can easily happen due to a configuration error) then you might end up in a situation in which no usable current backups exist.

That’s why I recommend setting up a lab environment that shares a similar configuration to your production network. This process allows you to set up, configure and thoroughly test your new backup solution prior to placing it on the production network.

It is important to test the new backup system, rather than trying to connect the new system and the existing backup system simultaneously. The reason is that when you run two different backup solutions against the same servers, the backup products will usually fight with one another. In the case of file servers, both solutions may attempt to manipulate the archive bit on your files. This bit is often used to determine what needs to be backed up. In the case of Exchange servers, one backup solution may process and then purge transaction log files before the other backup solution is able to make a backup.

As you perform your tests, keep in mind that there will likely be a period of coexistence when both your old and new backup systems exist on your network (although you will have to suspend your old backup jobs to avoid the problems mentioned earlier). You must take this situation into account as you test your new backup system, and make sure that the agents do not interfere with one another.

Determine your backup needs
The next step in the process is to determine your backup needs. You must review your existing backup logs to determine what is currently being backed up, and whether any changes need to be made. In doing so, it is easy to assume that you can ignore the current backup schedule since disk-based backups tend to perform backups in near real time. However, the backup schedule may reveal the unexpected. For instance, many companies are required to create and retain quarterly archives. Such archives must be kept separate from the regular backups.

Decide what to do with your tape hardware
The third step in the process is deciding what to do with your existing tape hardware. Getting rid of your old tape drives is not an option, because you have to be able to restore backups that were created with it.

One option is to connect your tape drive to your disk backup solution. That way, you can periodically dump your disk backups to tape for long-term data retention. Of course, if you are ever asked to restore any of your old tape backups, you will likely have to reconnect the tape drive to a computer that is running your old backup software.

This brings up another point: Be sure to keep an up-to-date copy of your old backup software in a safe place. In order to restore an archive tape, you will need to have a copy of the software that was used to create the archive.
Evaluate your long-term tape retention requirements
The next step in the process is to evaluate your long-term tape retention requirements. You probably have a mountain of tapes stored at an offsite facility. Eventually, you will probably be able to get rid of (or overwrite) some of these tapes but you will have to determine how long the tapes must be retained in order to meet your recovery goals.

Make the transition
Once you have thoroughly tested your new disk backup appliance and determined the impact of the transition on your network, it is time to move the new backup system from the lab to the production network. After doing so, don’t forget about your old backup software. Some administrators like to leave the old backup software installed in case they have to restore a file or even revert back to the old solution because of an unforeseen problem. While there is nothing wrong with leaving the old backup software installed, you do need to cancel or suspend the backup jobs so that they do not interfere with your new backup solution.

Make your first backup
Once your new backup solution is in place, you will have to run a full backup. Most of your future backups will be incremental, but your first backup will have to be a full backup which can take additional time to complete.

After your first backup is done, you must review the backup logs for any signs of trouble. You should also thoroughly test your ability to restore the data that has been backed up.

Monitor your backups
You should monitor your new backup solution’s disk space consumption rate and watch the logs for any sort of errors that may occur over the next several months.

 By: Brien M. Posey

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