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This question has got a bunch of us talking in chat, and it had me wondering:

Most of RAID 5's ugly characteristics like UREs and long rebuilds present themselves in much larger arrays. With a RAID 5, you'll have 66% disk space available and can sustain 1 disk failure. With a RAID 1E, you'll have 50% disk space available and can also sustain 1 disk failure.

Given a three disk array, in what case would it be preferable to use a RAID 1E over a RAID 5?

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up vote 6 down vote accepted

If you don't have a write cache, the parity calculation for writes, especially random writes, will be higher on raid-5 than some non-parity based raid like raid-1E.

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So, if you have a high write workload and, for some reason, are stuck with a 3-disk array to handle this workload and not enough write cache to overcome the write penalty, then RAID 1E would be a better solution? – MDMarra Jul 20 '12 at 19:05
Yeah, if you have enough random writes that your cache can't completely buffer them (or if you have writethrough enabled), something without parity calculations would be a way of getting around it. Raid 1E and raid 10 don't use parity. – Basil Jul 20 '12 at 19:38

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