On Fri, 22 Jul 2005 12:28:43 -0700 "Luke Lonergan" <[EMAIL PROTECTED]> wrote:
> Joshua, > > On 7/22/05 10:11 AM, "Joshua D. Drake" <[EMAIL PROTECTED]> wrote: > > The database server is a PE (Power Edge) 6600 > > > > Database Server IO: > > > > [EMAIL PROTECTED] root]# /sbin/hdparm -tT /dev/sda > > > > /dev/sda: > > Timing buffer-cache reads: 1888 MB in 2.00 seconds = 944.00 MB/sec > > Timing buffered disk reads: 32 MB in 3.06 seconds = 10.46 MB/sec > > > > Second Database Server IO: > > > > [EMAIL PROTECTED] root]# /sbin/hdparm -tT /dev/sda > > > > /dev/sda: > > Timing buffer-cache reads: 1816 MB in 2.00 seconds = 908.00 MB/sec > > Timing buffered disk reads: 26 MB in 3.11 seconds = 8.36 MB/sec > > [EMAIL PROTECTED] root]# > > Can you post the "time dd if=/dev/zero of=bigfile bs=8k count=500000" > results? Also do the reverse (read the file) with "time dd if=bigfile > of=/dev/null bs=8k". > > I think you are observing what we've known for a while, hardware RAID is > horribly slow. We've not found a hardware RAID adapter of this class yet > that shows reasonable read or write performance. The Adaptec 2400R or the > LSI or others have terrible internal I/O compared to raw SCSI with software > RAID, and even the CPU usage is higher on these cards while doing slower I/O > than linux SW RAID. > > Notably - we've found that the 3Ware RAID controller does a better job than > the low end SCSI RAID at HW RAID support, and also exports JBOD at high > speeds. If you export JBOD on the low end SCSI RAID adapters, the > performance is also very poor, though generally faster than using HW RAID. Are there any recommendations for Qlogic controllers on Linux, scsi or fiber channel? I might be able to my hands on some. I have pci-x slots for AMD, Itanium, or POWER5 if the architecture makes a difference. Mark ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org