Build a Linux Software RAID from Scratch - Page 3

Part Two: Last week we considered Linux software RAID's advantages, this week we show you how to do it.

 By Carla Schroder
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Continued From Page 2

Standby Spare Disk
You may add additional fault-tolerance by adding a standby spare disk. This only works in RAID levels with fault-tolerance, like RAID 1 and RAID 5. Don't bother with RAID 0, because if one disk fails the whole array is broken.

Simply install the extra disk, then add these lines to /etc/raidtab:

nr-spare-disks    1
device           /dev/hdd1
spare-disk        0

If all goes well, the standby disk will automatically take over when one of the other disks fail.

We covered a lot of ground in a short space here. Be sure to read The Software-RAID HOWTO for explanations of the options in /etc/raidtab. You'll also find the importance of chunk sizes for performance, and chunk-size gotchas with the Ext2/3 filesystem. And tools for monitoring and querying the array, simulating failures and other useful tests and refinements.



Updated: The examples in this article included a mistake in the commands used to create and prepare swap partitions for use. We've updated the examples. Thanks to the readers who notified us of the error.

This article was originally published on May 17, 2005
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