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Intel RAID5: pretty much worthless

I have a co-located server with a 3-disk RAID5 array (Intel ICH8 controller).  Things seemed fine when I was setting up the server – pull a disk drive, re-insert, volume rebuilds, everything keeps working.

What I didn’t test though is how degraded the performance is while rebuilding.  A disk array that was getting 100MB/s reads during normal operation is now getting < 1MB/s reads while rebuilding, and my database application can’t complete requests at that speed.  To add insult to injury, the completely idle server with all disks healthy takes over 100 hours to rebuild a 2TB volume (~5.8MB/s).

Googling reveals dozens of similar horror stories with Intel RAID5 rebuilding.  Do yourself a favor and rule out Intel’s RAID5 if you care about usable uptime.

Edit: I’ve changed to a 2-disk software RAID1 and am getting 80MB/s read during rebuilds.