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Hi, I think I had the same problem on a PIIX SATA with RAID1. Basically, I noticed that each disk could be accessed one at a time, and that it was totally impossible to access the second one while the first one was reading. A simple "cat /dev/sda >/dev/null" prevented anyone from logging into the box or doing anything which required disk I/O. So if you have the same problem, I can fairly understand your low numbers. Could you try something like : # cat /dev/sda >/dev/null & # hdparm -t /dev/sdb If hdparm doesn't start before the 'cat' ends, you do have the same problem. Well, I don't know where it comes from, and unfortunately I don't have the machine anymore to try fixes. Regards, Willy On Wed, May 26, 2004 at 03:46:57AM +0400, Andrey Nekrasov wrote: > Hello, > > controller - Promise SATA 150 TX4, linux 2.6.7-rc1-bk1, HDD Maxtor > 250Gb (x4) > > Why so slowly reads (and writes) with software raid5? > > gnome:~ # hdparm -t /dev/sda2 > > /dev/sda2: > Timing buffered disk reads: 148 MB in 3.01 seconds = 49.16 MB/sec > gnome:~ # hdparm -t /dev/sdb2 > > /dev/sdb2: > Timing buffered disk reads: 148 MB in 3.02 seconds = 49.01 MB/sec > gnome:~ # hdparm -t /dev/sdc2 > > /dev/sdc2: > Timing buffered disk reads: 148 MB in 3.03 seconds = 48.90 MB/sec > gnome:~ # hdparm -t /dev/sdd2 > > /dev/sdd2: > Timing buffered disk reads: 144 MB in 3.00 seconds = 47.96 MB/sec > gnome:~ # > gnome:~ # > gnome:~ # hdparm -t /dev/md0 > > /dev/md0: > Timing buffered disk reads: 64 MB in 3.12 seconds = 20.52 MB/sec > gnome:~ # > > > gnome:~ # cat /etc/raidtab > raiddev /dev/md0 > raid-level 5 > nr-raid-disks 4 > nr-spare-disks 0 > persistent-superblock 1 > parity-algorithm left-symmetric > chunk-size 1024 > > device /dev/sda2 > raid-disk 0 > > device /dev/sdb2 > raid-disk 1 > > device /dev/sdc2 > raid-disk 2 > > device /dev/sdd2 > raid-disk 3 > > > bye > -- > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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