Backups: An Important Part of Data Security
By Chuck Connell
Backups. This topic may seem boring, or obvious, but it is amazing how often I run into IT managers who aren't doing it right. Imagine that someone hacks into your computer system and deletes a very large number of files, with no way to recover the files later. You would certainly consider this a major security failure. Yet a disk crash, without proper backups, is the same thing.
There are four important elements to any good backup plan:
1) Perform incremental backups often, with full backups less often. This is standard procedure for most backup software, but is worth stating anyway. There is little reason to back up every file every night, since only a small percentage of files change each day. On the other hand, it is good to have a full backup every so often, since restoring files from incremental backups is a pain and can be prone to errors.
2) Use multiple sets of backup media. In other words, don't overwrite the same set of disks/tapes each night or each week. There are several reasons for this. Suppose that you have only one set of weekly backup media and keep reusing it. Now suppose that your backup process fails one week. You are completely vulnerable, since you have no full backup at all. Another reason is that a user may tell you on Thursday that they want to restore a file they had on Monday and Tuesday. If you have reused your daily media, you no longer have a backup of this file.
3) Take some backups off site and keep them for a long time. Backup media is very cheap and compact lately. CD-R's are now selling for about 30 cents each, and they are small when stacked together. You can store 70GB (100 CDs) in a stack about the size of two Big Macs. TR5 tapes are even smaller, although they cost more per gigabyte.
4) Test the backups! This is one of the biggest errors I see. Many IT managers feel secure in the belief that their staff is performing regular backups, only to be shocked when they actually try to use one of the backups and find that it does not work. There are many reasons that a backup may not have the files you think it does, including failure of the backup software, human error, and bad physical media. Every so often, delete a few unimportant files from your system. Then ask your IT staff to restore the files. You may be surprised what happens.
Putting all these pointers together yields a backup scheme that looks something like this… Create 20 sets of daily (incremental) backup media and four sets of weekly (full) backup media. Do an incremental backup each night Monday through Friday, and a full backup every weekend. Each set of media (daily and weekly) will be reused once per month. At the end of each month, take the latest full backup off site and keep it there for several years. Replace the full backup set with new media. Once per quarter, delete some files, and then attempt to restore them. Make sure some of the files were deleted just the day before, some the previous week, and some a month earlier. (This simulates what really happens when people ask to restore files.)
Of course, other variations on these ideas also are valid. Small organizations with low computer usage might do incremental backups weekly and full backups monthly. Some organizations store every week's backup off site. Some use remote backup procedures so backup media is always off site.
The key is to define a backup scheme that makes sense for your organization, and then stick with it.
Chuck Connell is president of
CHC-3 Consulting , which helps organizations with all aspects of Domino and Notes, especially administration and security. Chuck helps companies to outsource their Domino administration needs via the Web site DominoAdministration.com and runs the popular security site DominoSecurity.org .
