On Sat, 2005-08-20 at 15:54 -0700, Linda Walsh wrote:

This ended up way longer than I intended, but it covers several factors that can affect disk performance and I wanted to try to give you a complete as list as I could think of to look for areas of change, potential causes, etc. Sorry it ended up so long though, it's a complex subject and I probably forgot to mention some items as it is...:-).

This was hugely helpful. Thank you. I came in tonight to do some more controlled experimentation with two machines. One machine is SCSI based HW RAID. The other is IDE based SW RAID. On each machine I partitioned the disks like this: test1 partition 9.1 root swap test2 partition 9.3 root test3 partition I ran my 'dd' test three times on each partition from each SuSE version on the SCSI machine. The differences between 9.1 and 9.3 were small enough I cannot determine which one is faster. The IDE machine took so long to install 9.3 on, I took a break, checked my email and found this note from Linda. I discovered using hdparm that while both disks were using udma5, hda read speed was *much* slower than hdc. I used 'raidsetfaulty' to remove the slow drive from the RAID set and my hdparm reads and dd writes were vastly improved. Nearly all of the servers I have available to test on have already been upgraded to 9.3 and are IDE systems with SW RAID. The few comparable 9.1 machines I had to test were IDE systems, but not using SW RAID. Thus I incorrectly attributed the difference to the OS version. Thank you all for your help! -K