From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: Re: Did I make a mistake? Date: Fri, 20 May 2011 10:16:43 +0600 Message-ID: <20110520101643.37dffc49@natsu> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/Kct_YYhNTD/PwnKTC+ppiBf"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: lrhorer@satx.rr.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/Kct_YYhNTD/PwnKTC+ppiBf Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Thu, 19 May 2011 21:45:23 -0500 "Leslie Rhorer" wrote: > OK, I may have made an error, and I want to make sure before this > goes any further. Yesterday I created a RAID6 volume with eight 3TB > members, on the same machine containing an older RAID6 array built of > fourteen 1G members. Based upon my reading here and some level of > experience with larger stripe sizes, I decided to create the array with a > chunk size of 4096K. 4096K is an absurdly large chunk for such RAID5/RAID6 array, I wanted to re= fer some benchmarks, but couldn't even find any that would test such a huge chu= nk, largest they test is 1024 or 2048, where the write performance already drops off very sharply, e.g. see: http://blog.jamponi.net/2008/07/raid56-and-10-benchmarks-on-26255_10.html http://louwrentius.blogspot.com/2010/05/raid-level-and-chunk-size-benchmark= s.html While the read performance does seem to not suffer or even increase at higher chunk size, the best read/write combination performance seems to be achieved at 64...256K chunk for RAID5/6. If you decide to persist with the current configuration, make sure you increase stripe_cache_size by a lot (and btw raising it if you have the RAM to spare is a good idea in any case). --=20 With respect, Roman --Sig_/Kct_YYhNTD/PwnKTC+ppiBf Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEARECAAYFAk3V6ysACgkQTLKSvz+PZwgYKwCfUVTNDxqab1wLUvCUXWddWP7y JMMAnjTW6P4/oqGMJTwyK/SwDZ4qoYAt =eALL -----END PGP SIGNATURE----- --Sig_/Kct_YYhNTD/PwnKTC+ppiBf--