On 12/20/05, Christian Motta <chris@xxxxxxxxx> wrote: > After seeing many of these threads I compared what my server tested at > (mounted) > and now I am concerned about my own results. > > My raid is raid 1 w/ 2 300gb Western Digital SATA/7200/8 hard drives > > # /sbin/hdparm -t /dev/md4 > > /dev/md4: > Timing buffered disk reads: 172 MB in 3.00 seconds = 57.32 MB/sec > > so if I am reading this correctly my hard drives are half the speed of my > nic card???? > > Is that correct? > > -chris > > > > > > Chris Eborn wrote: > 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 > > > Hi There, > Well I am still suffering with this - I have installed Fedora Core 2 > with kernel 2.6.14 and the raid is still going half speed. > I have spent quite a while playing with the readahead values (blockdev > --setra) on both the individual disks and the raid device (/dev/md0) > and they do not seem to change anything, even with extreme values > (like "blockdev --setra 0 /dev/sd[abcdefghi]"). Leads me to think that > readahead has been disabled elsewhere. Hi Christian, It may well be worth testing with a proper utility like iozone or bonnie as well. Could you test the read speed of a single disk? hdparm -t /dev/hda My single disk will do around 60MB/sec (10,000rpm scsi disks:-) Chris
