Where DIY belongs

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The question of: "When should you built it your self and when should you get it off the shelf?" is one that varies from workplace to workplace. We heard several different variants of that when were interviewing for the Vice Provost for IT last year. Some candidates only did home-brew when no off the shelf package was available, others looked at the total cost of both and chose from there. This is a nice proxy question for, "What is the role of open source in your environment," as it happens.

Backups are one area where duct tape and bailing wire is to be discouraged most emphatically.

And now, a moment on tar. It is a very versatile tool, and is what a lot of unixy backup packages are built around. The main problem with backup and restore is not getting data to the backup medium, it is keeping track of what data is on which medium. Also in these days of the backup-to-disk, de-duplication is also in the mix and that's something tar can't do yet. So while you can build a tar-and-bash backup system from scratch without paying a cent, it will be lacking in certain very useful features.

Also? Tar doesn't work nearly as well on Windows.

Your backup system is one area you really do not want to invest a lot of developer creativity. You need it to be bullet proof, fault tolerant, able to handle a variety of data-types, and easy to maintain. Even the commercial packages fail some of these points some of the time, and the home brew systems fall apart much more often relative to these. The big backup boys have agents that allow backups of Oracle DBs, Linux filesystems, Exchange, and Sharepoint all to the same backup system, a home-brew application would have to get very creative to do the same thing; the problem gets even worse when it comes to restore.

Disaster Recovery is another area in which duct tape and bailing wire are to be discouraged most emphatically.

There are battle-tested open-source packages out there that will help with this (DRBD for one), depending on your environment. They're even widely used so finding someone to replace the sysadmin who just had a run in with a city bus is not that hard. Rsync can do a lot as well, so long as the scale is small. Most single systems can have something cobbled together.

Problems arise when you start talking Windows, very complex installations, or money is a major issue. If you throw enough money at a problem, most disaster recovery problems become a lot less complex. There is a lot of industry investment in DR infrastructure, so the tools are out there. Doing it on a shoe-string means that your disaster recovery also hangs by a shoe-string. If you're doing DR just to satisfy your auditors and don't plan on ever actually using it, that's one thing. But if you really expect to recover from a major disaster on that shoe-string you'll be sorely surprised when that string snaps.

Business Continuity is an area where duct tape and bailing wire should be flatly refused.

BC is in many ways DR with a much shorter recovery time. If you had problems getting your DR funded correctly, BC shouldn't even be on the timeline. Again, if it is just so you can check a box on some audit report, that's one thing. Expecting to run on such a rig is quite another.

And finally, if you do end up cobbling together backup, disaster recovery, or business continuity systems from their component parts, testing the system is even more important. In many cases testing DR/BC takes a production outage of some kind, which makes it hard to schedule tests. But testing is the only way to find out if your shoe-string can stand the load.

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