PE2650 w/ PERC3/QC + PowerVault 220S Performance Issues
comsatcat at earthlink.net
Thu May 13 17:19:00 CDT 2004
I am having (as it seems a lot of other people are) performance issues with the dell poweredge 2650's w/ perc controllers and powervault storage. First let me give you my current configuration:
OS: Red Hat Enterprise Linux 3 Advanced Server
Powervault: 220S in Split mode, raid 5 across 4 channels, 128k stripe size, 1 hotspare (1.8TB logical disk), Each drive is a 72gig 10k scsi drive.
Perc: Write Policy WRBACK, Read Policy is Adaptive, and Cache Policy is DirectIO.
Filesystem: ext2 blocksize 4096, 1 inode per 256k block, atime disabled.
The filesystem structure will consist of exactly 54 directories, each of which containing 15 two gigabyte files which will be written to more then read. Average record written to disk will be 256k.
I am currently getting 15meg/sec via iostat w/ a very high await time (800 - 1200ms) at 100% utilization. I've tried configuring the drives many differnet ways... as one large volume, 4 smaller 400gig volumes, and a straight through non raid (well it had to be raid 0 as I can't figure out how to get the device to just allow access to the dsisks with out creating a logical disk for each one).
I achieved the best performance writing to a single 2gig file on a single raid0 disk (1 physical drive), however this is not a solution as I need the data integrity that raid 5 provides. I was able to achieve close to equiv performance when using a 1.8tb volume of raid5, but when it comes to simultanious writes to multiple files, performance drops down to 15megs/sec.
The performance I'm getting is absolutely rediculous for a direct connect scsi device, especially raided. I've read over the past 8 or so months of the list, no one has seemed to come up with a solution for this problem.
Besides the obvious of updating firmware/drivers/kernel, what configuration changes can I make or debugging steps can I take to remedy the situation?
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