<div class="gmail_quote">On Wed, Mar 17, 2010 at 11:45 AM, Graham Mitchell <span dir="ltr"><<a href="mailto:gmitch@woodlea.com">gmitch@woodlea.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">> With 4 drives you would be better using RAID 0+1<br>
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</div>Probably better off using RAID 1+0 (a stripe of mirrors), rather than 0+1 (a<br>
mirror of a stripe)<br></blockquote><div><br>Yes. Just to elaborate, the difference is in what happens when you lose a drive. With raid 0+1 if you lose a drive you lose the entire stripe - you're effectively back to a raid 0. With raid 1+0 if you lose a drive you've got one degraded mirrored pair but the rest of the mirrors in the stripe are still at full performance. However it's possible that mdadm is actually smart enough to handle these two cases identically anyway (but I'm not 100% sure).<br>
<br>With mdadm you'd be better off using raid10 which manages striping and mirroring together at the block level. It's both more flexible and potentially better performing. Basically it spreads X copies of the data over Y drives with the copies staggered physically. Look it up on wikipedia for more details.<br>
<br>Cheers,<br>Steve<br></div></div>