<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> 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: <blockquote cite="mid68fef4480512200827n4dd63e77h9cbda6f198519820@mail.gmail.com" type="cite"> <pre wrap="">On 12/15/05, Gilboa Davara <a class="moz-txt-link-rfc2396E" href="mailto:gilboada@netvision.net.il"><gilboada@netvision.net.il></a> wrote: </pre> <blockquote type="cite"> <pre wrap="">On Thu, 2005-12-15 at 17:07 +0000, Chris Eborn wrote: </pre> <blockquote type="cite"> <pre wrap="">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 </pre> </blockquote> <pre wrap="">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 </pre> </blockquote> <pre wrap=""> 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. Chris ps - Unfortunately this machine needs to be able to show 24 12 meg files a second (that's because film runs at 24fps) - so come the new year it may well have to fall into the windows empire :-( </pre> </blockquote> </body> </html>