On Fri, Jul 29, 2005 at 01:11:35PM -0700, Mark Wong wrote: > On Fri, 29 Jul 2005 14:57:42 -0500 > "Jim C. Nasby" <[EMAIL PROTECTED]> wrote: > > > On Fri, Jul 29, 2005 at 12:51:57PM -0700, Mark Wong wrote: > > > > Not sure I fully understand what you're trying to say, but it seems like > > > > it might still be worth trying my original idea of just turning all 80 > > > > disks into one giant RAID0/striped array and see how much more bandwidth > > > > you get out of that. At a minimum it would allow you to utilize the > > > > remaining spindles, which appear to be unused right now. > > > > > > I have done that before actually, when the tablespace patch came out. I > > > was able to get almost 40% more throughput with half the drives than > > > striping all the disks together. > > > > Wow, that's a pretty stunning difference... any idea why? > > > > I think it might be very useful to see some raw disk IO benchmarks... > > A lot of it has to do with how the disk is being accessed. The log is > ideally doing sequential writes, some tables only read, some > read/writer. The varying access patterns between tables/log/indexes can > negatively conflict with each other.
Well, seperating logs from everything else does make a lot of sense. Still interesting that you've been able to see so much gain. > Some of it has to do with how the OS deals with file systems. I think > on linux is there a page buffer flush daemon per file system. A real OS > person can answer this part better than me. So, about testing with FreeBSD.... :P -- Jim C. Nasby, Database Consultant [EMAIL PROTECTED] Give your computer some brain candy! www.distributed.net Team #1828 Windows: "Where do you want to go today?" Linux: "Where do you want to go tomorrow?" FreeBSD: "Are you guys coming, or what?" ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend