From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: Re: raid6 low performance 8x3tb drives in singledegraded mode(=7x3tb) Date: Wed, 19 Sep 2012 13:40:30 +0600 Message-ID: <20120919134030.222e4b04@natsu> References: <504FD153.9090602@sandberg-consult.dk> <20120919162557.03df6af2@notabene.brown> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/93cB.bcZssf37NM0X5SOJvI"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20120919162557.03df6af2@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: Kasper Sandberg , linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/93cB.bcZssf37NM0X5SOJvI Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 19 Sep 2012 16:25:57 +1000 NeilBrown wrote: > RAID5/RAID6 write speed is never going to be brilliant, but there probabl= y is > room for improvement. Hopefully one day I figure out how to effect that > improvement. "/sys/block/md*/md/stripe_cache_size" is absolutely the first thing one sho= uld look at when facing a problem with md RAID5/6 write performance. It is understandable that the default value can't be high (as it consumes a lot of RAM on large disk counts), but increasing it if you have the RAM can increa= se the write speed by 200 to 400%: http://peterkieser.com/2009/11/29/raid-mdraid-stripe_cache_size-vs-write-= transfer/ --=20 With respect, Roman ~~~~~~~~~~~~~~~~~~~~~~~~~~~ "Stallman had a printer, with code he could not see. So he began to tinker, and set the software free." --Sig_/93cB.bcZssf37NM0X5SOJvI Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlBZdu4ACgkQTLKSvz+PZwhNbwCgi8jH9dqR7hz4xq51C9imz3j9 X2cAn1FgCKvDLSylwwMarBLQa31UXWrN =yQdu -----END PGP SIGNATURE----- --Sig_/93cB.bcZssf37NM0X5SOJvI--