On Thu, 23 Dec 2010, Andrew Hume wrote:
we (some folks at work) have built two backblaze boxes (roughly speaking, a linux box with 45 2TB drives).i think i know how to deploy such a beast, but wanted to check my understanding, which is that mdadm is the tool of choice, and that for performance and reliability, raid10 is the sweet spot (specificly, not RAID5). does anyone have anything specific to say about mdadm, and the raid it produces, either good or bad?
mdadm has by far the longest track record, with the most raid support. there is also the dm family of drivers and tools which have some additional features.
which raid mode you want is highly dependent on what your requirements are and how much space you are willing to sacrafice.
raid6 is significantly more reliable than raid5, raid1, or raid10, but suffers the same write performance issues that raid5 has (note that if you are in something close to a read-only situation, raid6 can be just as fast as raid10 while still being more reliable, it's what I use for my splunk datastore for example)
raid5 and raid6 really suffer in the situation where you have lots of small, random writes. large sequential writes have much less overhead.
David Lang
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