This sounds like a bad RAID controller - are you using a built-in hardware RAID? If so, you will likely want to use Linux software RAID instead.
Also - you might want to try a 512KB readahead - I've found that is optimal for RAID1 on some RAID controllers. - Luke On 5/30/07 2:35 AM, "Albert Cervera Areny" <[EMAIL PROTECTED]> wrote: > Hi, > after doing the "dd" tests for a server we have at work I obtained: > Read: 47.20 Mb/s > Write: 39.82 Mb/s > Some days ago read performance was around 20Mb/s due to no readahead in md0 > so I modified it using hdparm. However, it seems to me that being it a RAID1 > read speed could be much better. These are SATA disks with 3Gb of RAM so I > did 'time bash -c "dd if=/dev/zero of=bigfile bs=8k count=786432 && sync"'. > File system is ext3 (if read many times in the list that XFS is faster), but > I don't want to change the file system right now. Modifing the readahead from > the current 1024k to 2048k doesn't make any difference. Are there any other > tweaks I can make? > > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org > ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
