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When the lights go out: Exchange disaster recovery, part 2

Here's some advice on what tools and methods you can use to back up and restore your Exchange servers--as well as what methods you should avoid. Part 2 of 2-part series.

In Part 1 yesterday, I discussed the basic tools you can use for disaster recovery. Today I am going to talk about the different ways that Exchange (and Exchange servers) can be backed up and restored.

If you find yourself in need a major recovery, Exchange 2003 admins should use the newest version of EXMerge, now known as the Mailbox Merge Wizard.

EXMerge is the standard tool for extracting e-mail from one server and moving it to another. The Exchange 2003 version can be run to extract mail from any version of Exchange, but should only be run on a computer that is itself running Exchange 2003. This makes it easier to move mail in either direction should the need arise. The Mailbox Merge Wizard can be downloaded here.

Backup strategies
A "brick-level backup" is Exchange-admin slang for any backup of the entire Exchange Information Store (IS) done through a MAPI client. It gets its name because the whole store is backed up as a single "brick" of information.

People do brick-level backups because they're easy. If anything goes wrong, you can simply pull individual folders from the brick-level backup without having to restore the whole IS. The problem with this approach is threefold:

1) Restoring from a brick-level backup is slow, since the backup process has to traverse each mail item individually, incurring unneeded overhead. Also, redundant copies of each message are kept for each of its recipients, and you cannot restore individual mail items without restoring an entire folder and picking out only the needed items.

2) Restoring a single mailbox out of context from the rest of the IS can create problems that you can't correct manually. Often during the backup process, the backup program will warn (spuriously) that certain files are corrupt, and the user may set the program to ignore all such warnings. This causes genuine corruption problems to be ignored, which results in the entire backup being useless.

3) Brick-level backups cannot be used for effective disaster recovery. If for no other reason, this is why brick-level backups are all but a waste. If the lights go out and the server is trashed, a brick-level backup cannot help you bring the mail store back online without incurring terrible problems.

4) Brick-level backups are done through the MAPI interface, which was designed to transfer mail and not to perform backup operations.

My advice to you is:

-- Don't use brick-level backups. Brick-level backups are backups of the entire Exchange Information Store (IS) as done through a MAPI client. This is not only the wrong tool for the wrong job, but the way brick-level backups are made and stored create more problems than can be discussed here. Never use them for disaster recovery, either, as they won't be enough to get you back from the brink of death.

-- Use file-level offline backups with an Exchange-aware backup program. The exact style of backup is totally up to you: it can be across a network to another computer, into a SAN (Storage Area Network), to tape or even to DVD+R if you're so inclined. The important thing is that you use a backup program that is Exchange-aware.

Two of the most common third-party Exchange-aware backup tools are Veritas's Backup Exec and Computer Associates's Arcserve, both of which are Exchange 2003 compatible. Arcserve is the more broadly used of the two, but administrators seem to prefer Backup Exec because it is faster (especially in its 9.0 incarnation), easier to work with and more coherently documented.

If you're stuck with what you have lying around, even the lowly NTBACKUP tool will work for Exchange backups. Use the ds and is command-line switches when invoking the program to back up or restore the Directory Store and the Information Store, respectively.

One ingenious backup method I've seen used is NTBACKUP to back up the stores not to tape but instead to another machine across the network, where the files were split off into 4.5GB pieces and copied to several DVD+RWs once a week. The entire operation, save for copying to DVD, was totally unattended. (This was done because there was no tape drive handy, but there was a DVD+RW burner.)

To read Part 1, click here.

Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.

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