Date: Wed, 20 Apr 2016 10:23:31 +0100 From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-questions@freebsd.org Subject: Re: Raid 1+0 Message-ID: <5027ef1b-fd33-5e07-3a8d-fe0ce9732b29@freebsd.org> In-Reply-To: <44a8kpcm14.fsf@be-well.ilk.org> References: <571533F4.8040406@bananmonarki.se> <57153E6B.6090200@gmail.com> <20160418210257.GB86917@neutralgood.org> <64031.128.135.52.6.1461017122.squirrel@cosmo.uchicago.edu> <20160419153824.7b679129f82a3cd0b18b9740@sohara.org> <40267.128.135.52.6.1461098148.squirrel@cosmo.uchicago.edu> <44a8kpcm14.fsf@be-well.ilk.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --8JPBdPjffXrHQaBHhtwNnxDBAv7ScOJOb Content-Type: multipart/mixed; boundary="AlJjkGSRPRdAPP0imDvgQgnbX8EdmxIEv" From: Matthew Seaman <matthew@freebsd.org> To: freebsd-questions@freebsd.org Message-ID: <5027ef1b-fd33-5e07-3a8d-fe0ce9732b29@freebsd.org> Subject: Re: Raid 1+0 References: <571533F4.8040406@bananmonarki.se> <57153E6B.6090200@gmail.com> <20160418210257.GB86917@neutralgood.org> <64031.128.135.52.6.1461017122.squirrel@cosmo.uchicago.edu> <20160419153824.7b679129f82a3cd0b18b9740@sohara.org> <40267.128.135.52.6.1461098148.squirrel@cosmo.uchicago.edu> <44a8kpcm14.fsf@be-well.ilk.org> In-Reply-To: <44a8kpcm14.fsf@be-well.ilk.org> --AlJjkGSRPRdAPP0imDvgQgnbX8EdmxIEv Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 04/19/16 22:43, Lowell Gilbert wrote: > Correlation is not causation. >=20 > It's not a big stretch to imagine that two nearly identical mechanical > devices, operated in nearly identical conditions, might wear out in a > nearly identical way at about the same time. There is no need for one > drive to affect the other. Interestingly this argument is quite a bit stronger when applied to SSD's rather than spinning disk drives. SSDs we know have a limited number of refresh cycles for any one memory cell. As members of a RAID array, they're going to see very similar patterns of activity over their lifetimes, so they're actually quite likely to wear out at a similar time= =2E > A fair number of people believe that this in fact occurs. I've looked > for evidence on the subject, and I haven't found anything (beyond > anecdotes) for or against the possibility. Mechanical drives are a lot more affected by external differences like vibration or temperature changes, which will act to increase the variability in their lifetimes. SSDs are intrinsically /more/ reliable during their working life, but their lifetime tends to come to a much more sharply defined end. Cheers, Matthew (who has been spending far too much time going to the datacentre to replace drives recently.) --AlJjkGSRPRdAPP0imDvgQgnbX8EdmxIEv-- --8JPBdPjffXrHQaBHhtwNnxDBAv7ScOJOb Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJXF0qaAAoJEABRPxDgqeTnKA4P/R1mtBargXP3BrpJyKtI3KLS pVS/26BAuLfPxVq/U/EK8wp5dEsUziCIh9lrZgwLS8OxTYaB3kfZO11kM49XMu/Y B8wQmnnVjeG18HlYaHRPcvJ1ELDe8TD334t/RzXTK4clnYqMmJl5Df6UZbOXUCIL dAbzW0nNhcsClqpZV4xBvGn1ZAGfK9aFTmofqN+4eZUqd+A9YROjBqzzpFzRCnDR BDJ9tuVctVlnt/iMiG+bvlrWkw7m2X8HEajGLjnLYz659xUp2S+WsK+KvKaXOcql oqZWTKYV1CmeAbBxYov9vxesewfMhFmfK9Mdg/318+IDxzY4V0mPdNM0qROBQJG4 O8bWfyrV+bm0y3aC4dkLj+GzC2RtRXAIH4p2Q6bzKnrU8HHlv4dSKRSzpPH1/948 /IbkHby3wnZZmwhoJYRGGVo0EJbNLDaCkjzUBKgw1zO6yxAqvyIeIfdtbsjjGDnJ 6zABr0wvQkg6s2GVR1kGYmaeJkoVJndH6Ez0mg26NRQOlwTElJgTWPMvTtaLns0q pOIAj57fLTXiOccK5codnzab3j4HLf9oYkNi8Jm2TjcpFsO5tpbFuBDJ2ZAomRez LIEJffXPwAOAdyMhJ0ljW2HHMrtl1Ib7dcxjYBFxNWvrxz+RFXYZ18p+CAj01LRU tbtT+KZIGIV70g7TN6ev =hjLE -----END PGP SIGNATURE----- --8JPBdPjffXrHQaBHhtwNnxDBAv7ScOJOb--
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