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Drive Failure In RAID 1 Or RAID 0,1 Situations

Fast and Inexpensive - Promise's FastTrak66 IDE RAID-Controller
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We have just learned that RAID 1 or mirroring is using half of the hard drives in an array to keep an identical image of your data, thus making your data a lot less sensitive to hard drive failures. Let's see how FastTrak66 handles a failing drive when running a RAID 1 or RAID 0,1 array.

We simulated a hard drive failure by simply pulling the power connector of one drive while the system was running. Here the FastTrak66 showed one major flaw that is due to its IDE support. A SCSI RAID controller wouldn't have this problem.

The failure of one drive in a RAID 1 or RAID 0,1 configuration will in most cases cause the other drive connected to the same channel to fail as well. The reason for this behavior is rather simple. Most drives, es e.g. IBM and WD hard drives, have different jumper settings for 'single drive', 'master drive' and 'slave drive'. If one hard drive of the same channel fails, the other slave or master drive suddenly becomes a 'single drive'. Unfortunately the jumper settings of the drive don't represent that status and so it fails as well. This means that you must run 1:1 mirrors only by connecting each drive to a different IDE channel , because otherwise both drives will fail and you won't get anything out of the mirror-situation.

Here is what happens if one drive fails in a 2:2 RAID 0,1 mirror of stripes configuration:

The monitoring utility reports both drives of this channel as failed. This is not so bad, because FastTrak mirrors across channels, so your data won't be lost. However, both drives need to be rebuild again.

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