Re: postgresql random io test with 2 SSD Kingston V+100 500GB in (software) Raid1

Am 19.04.2011 11:15, schrieb Laurent Laborde:
> Soft RAID1 (md)
> ext3

We have experimented a bit with Postgres and ext3 (with and without Linux
software RAID1) and have found that since somewhere after 2.6.18, it has been
prohibitively slow and causing high latencies during buffer flushes. You will
probably see a significant improvement with ext4 (mkfs.ext4, not just remount as
ext4, which is also possible).

Also, you need to make sure that your blocks are properly aligned with SSDs,
that might explain low random I/O performance. See
http://www.nuclex.org/blog/personal/80-aligning-an-ssd-on-linux and

http://www.ocztechnologyforum.com/forum/showthread.php?54379-Linux-Tips-tweaks-and-alignment&p=373226&viewfull=1#post373226

for example.

Regards,
  Marinos