From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Hill Subject: Re: High IO Wait with RAID 1 Date: Fri, 13 Mar 2009 09:39:38 +0000 Message-ID: <20090313093938.GA19733@cthulhu.home.robinhill.me.uk> References: <7d86ddb90903121646q485ad12y90824a4c3fcc2dfd@mail.gmail.com> <20090313004802.GB29989@mint.phcomp.co.uk> <7d86ddb90903122021y5f4f0868na3f1944f87f77f4a@mail.gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="9jxsPFA5p3P2qPhR" Return-path: Content-Disposition: inline In-Reply-To: <7d86ddb90903122021y5f4f0868na3f1944f87f77f4a@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids --9jxsPFA5p3P2qPhR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu Mar 12, 2009 at 10:21:28PM -0500, Ryan Wagoner wrote: > I'm glad I'm not the only one experiencing the issue. Luckily the > issues on both my systems aren't as bad. I don't have any errors > showing in /var/log/messages on either system. I've been trying to > track down this issue for about a year now. I just recently my the > connection with RAID 1 and mdadm when copying data on the second > system. >=20 > Unfortunately it looks like the fix is to avoid software RAID 1. I > prefer software RAID over hardware RAID on my home systems for the > flexibility it offers, especially since I can easily move the disks > between systems in the case of hardware failure. >=20 > If I can find time to migrate the VMs, which run my web sites and > email to another machine, I'll reinstall the one system utilizing RAID > 1 on the LSI controller. It doesn't support RAID 5 so I'm hoping I can > just pass the remaining disks through. >=20 You could also try using software RAID 10 or RAID 5 on the two drives. Both of these will be effectively the same as a RAID 1 (ISTR you can actually just update the metadata to convert from a RAID 1 to a RAID 5) but will use a different code path so should eliminate the issue you're seeing. A 2 drive RAID 10 with far layout will also give some read performance improvements (at the cost of slightly slower writes). Cheers, Robin --=20 ___ =20 ( ' } | Robin Hill | / / ) | Little Jim says .... | // !! | "He fallen in de water !!" | --9jxsPFA5p3P2qPhR Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkm6KdkACgkQShxCyD40xBJkwACffgBv8K1dX78y7ZK0Cl3K1VKy GP0AoMI1drd1UhyZm2QfU9mv1J+7rDCt =J6PK -----END PGP SIGNATURE----- --9jxsPFA5p3P2qPhR--