From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Zhang Subject: raid0 low performance Date: Thu, 30 Jun 2005 22:15:48 -0400 Message-ID: <1120184148.5521.21.camel@localhost.localdomain> Reply-To: mingz@ele.uri.edu Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-Rb4nCNAp8MfXD1OwPUeO" Return-path: Sender: linux-raid-owner@vger.kernel.org To: Linux RAID List-Id: linux-raid.ids --=-Rb4nCNAp8MfXD1OwPUeO Content-Type: text/plain Content-Transfer-Encoding: quoted-printable I meet some strange low performance when run RAID0 with vanilla kernel 2.4.27/2.6.11.12. My box is a 2.8G P4 and 1G RAM. 8 400GB SATA disk and A marvel 8port controller. I run marvel 3.4.1 driver. I wrote a small program to write device sequentially and SYNCHRONOUSLY. This is performance of 1 disk. looks fine. 1048576Bytes * 1024 : 55.466MB/s 524288Bytes * 2048 : 55.830MB/s 262144Bytes * 4096 : 55.782MB/s 131072Bytes * 8192 : 55.567MB/s 65536Bytes * 16384 : 55.926MB/s 32768Bytes * 32768 : 54.344MB/s 16384Bytes * 65536 : 41.415MB/s 8192Bytes * 65536 : 26.499MB/s 4096Bytes * 65536 : 15.110MB/s 2048Bytes * 65536 : 8.422MB/s 1024Bytes * 65536 : 4.318MB/s But when run 2 disk raid0, there is only 10% improvement. md3 : active raid0 sdb[1] sda[0] 781422592 blocks 64k chunks 1048576Bytes * 1024 : 67.300MB/s 524288Bytes * 2048 : 66.796MB/s 262144Bytes * 4096 : 65.728MB/s 131072Bytes * 8192 : 65.017MB/s 65536Bytes * 16384 : 59.223MB/s 32768Bytes * 32768 : 49.766MB/s 16384Bytes * 65536 : 39.162MB/s 8192Bytes * 65536 : 26.386MB/s 4096Bytes * 65536 : 15.084MB/s 2048Bytes * 65536 : 8.383MB/s 1024Bytes * 65536 : 4.303MB/s And when use 4 disks, the speed is slower! md0 : active raid0 sdh[3] sdg[2] sdf[1] sde[0] 1562845184 blocks 64k chunks 1048576Bytes * 1024 : 58.032MB/s 524288Bytes * 2048 : 56.994MB/s 262144Bytes * 4096 : 58.289MB/s 131072Bytes * 8192 : 65.999MB/s 65536Bytes * 16384 : 59.723MB/s 32768Bytes * 32768 : 50.061MB/s 16384Bytes * 65536 : 38.689MB/s 8192Bytes * 65536 : 26.169MB/s 4096Bytes * 65536 : 15.169MB/s 2048Bytes * 65536 : 8.378MB/s 1024Bytes * 65536 : 4.287MB/s Any hint on this? * I do not know how to check current PCI bus speed and I am not sure whether is limited by that. It is a 64bit card but I am not sure if it is run at 66MHZ. Should be, but want to check to make sure. * I tested each disk and all disk performs OK. Thanks Ming --=-Rb4nCNAp8MfXD1OwPUeO Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (GNU/Linux) iD8DBQBCxKdUSYbkL5BnVYoRAoLwAJwMcXhzJo+Qy9SofURGRRa1yFGZwACfZjwa bt01iS4gG37mwASq+iXCHTQ= =aV9S -----END PGP SIGNATURE----- --=-Rb4nCNAp8MfXD1OwPUeO--