On 12/15/05, Gilboa Davara <gilboada@xxxxxxxxxxxxxxxx> wrote: > On Thu, 2005-12-15 at 17:07 +0000, Chris Eborn wrote: > > Does the output from the following commands seem odd to people? > > > > [root@nucoda root]# hdparm -t /dev/md0 > > > > /dev/md0: > > Timing buffered disk reads: 774 MB in 3.01 seconds = 257.52 MB/sec > > [root@nucoda root]# mount /dev/md0 /array > > [root@nucoda root]# hdparm -t /dev/md0 > > > > /dev/md0: > > Timing buffered disk reads: 416 MB in 3.00 seconds = 138.55 MB/sec > > [root@nucoda root]# umount /array > > [root@nucoda root]# hdparm -t /dev/md0 > > > > /dev/md0: > > Timing buffered disk reads: 776 MB in 3.01 seconds = 257.42 MB/sec > > [root@nucoda root]# > > > > > > Tha array is made of 10 scsi disks - each of which will read at around > > 60 MB/sec and all seems fine with the raid > > device until the fs is mounted and it appears to halve the trasnfer > > rate! There is no activity in the filesystem. At the moment this > > is with FC2, though I have tried with FC3 and numerous kernels. > > Tweaking around with block sizes and thing does change the speed of > > the raw /dev/md0 - but the speed always drops when I mount the > > filesystem. Can anybody explain this behaviour? > > Maybe I am missing something obvious, but this is baffling me - and > > what is worse is that it all worked until I upgraded the system. I > > have tried to go back, even put a new system disk in and started from > > scratch, but cannot get a decent read speed from the array. > > > > Chris > > > > I'm seeing the same behavior on my 4x36GB MD5 setup. > Mounted FS: ~105-110MB/s. > Unmount FS: ~125MB/s. > > Can you check the read-ahead settings (blockdev --getra /dev/md0) > before /and/ after fs mount? > > Gilboa > > -- > fedora-list mailing list > fedora-list@xxxxxxxxxx > To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list > Hi Gilboa, [root@nucoda root]# blockdev --getra /dev/md0 2147483647 [root@nucoda root]# raidstart --all [root@nucoda root]# mount /dev/md0 /array [root@nucoda root]# blockdev --getra /dev/md0 1024 [root@nucoda root]# Also: [root@nucoda root]# blockdev --setra 4096 /dev/md0 BLKRASET: Invalid argument [root@nucoda root]# blockdev --setra 256 /dev/md0 BLKRASET: Invalid argument [root@nucoda root]# blockdev --setra 255 /dev/md0 [root@nucoda root]# Interesting! I was away on Friday, just back now. I will investigate this immeadiately. Thanks for the tip. Chris
