From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Hill Subject: Re: raid6 + caviar black + mpt2sas horrific performance Date: Wed, 30 Mar 2011 14:42:29 +0100 Message-ID: <20110330134228.GA14556@cthulhu.home.robinhill.me.uk> References: <20110330080823.GA9167@apartia.fr> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="7AUc2qLy4jB3hD7Z" Return-path: Content-Disposition: inline In-Reply-To: <20110330080823.GA9167@apartia.fr> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids --7AUc2qLy4jB3hD7Z Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed Mar 30, 2011 at 10:08:23AM +0200, Louis-David Mitterrand wrote: > Hi, >=20 > I am seeing horrific performance on a Dell T610 with a LSISAS2008 (Dell > H200) card and 8 WD1002FAEX Caviar Black 1TB configured in mdadm raid6. >=20 > Besides hardware, the other difference between servers is that the > PE2900's MegaRAID has no JBOD mode so each disk must be configured as a > "raid0" vdisk unit. On the T610 no configuration was necessary for the > disks to "appear" in the OS. Would configuring them as raid0 vdisks > change anything? >=20 Several years ago I ran into a similar issue with a SCSI RAID controller (may have been LSI MegaRAID, I can't recall now) and found that RAID0 vdisks were substantially faster than running it in JBOD mode. This wasn't just down to the controller disabling caching/optimisations either - in JBOD mode the performance was well below that on a non-RAID controller. Cheers, Robin --=20 ___ =20 ( ' } | Robin Hill | / / ) | Little Jim says .... | // !! | "He fallen in de water !!" | --7AUc2qLy4jB3hD7Z Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (GNU/Linux) iEYEARECAAYFAk2TM0MACgkQShxCyD40xBLbmQCcDfBwl4+2LGDCCcGvYeyh+EbK FpsAoNlmKfDBOTzL7FvSBb45pbMITsM6 =HIbM -----END PGP SIGNATURE----- --7AUc2qLy4jB3hD7Z--