Raid1 read performance.
pmueller at sidestep.com
Mon Apr 25 12:16:40 CDT 2005
> I'm a bit confused about read performance on my PERC4/SC
> PERC4e/DC PERC4e/Di
> controllers. When running in raid1 config I don't get better
> read performance than write performance.
> On my HP servers (also running raid1) I get about 2x read
> performance compared to write performance.
I am seeing this same behavior on RAID5 setups. I even purchased an LSI
megaraid320-2x and it had the same problem. Write speed was 120kbytes/sec on
a 7 disk-10k array. Read speed was ~25-30kbytes/s.
> Looks like the PERC controllers only us one disk for reads???
> Anybody seen the same, and have a remedy for this?
My servers were always remote when I was doing tests. This sounds likely,
though. Were you looking at the lights to figure this out?
> By the way, it doesn't matter if I change megaraid driver,
> still the same ratio.
I have updated the firmware, driver, ext3 mount options, etc., in all
combinations. Upgrading to the LSI firmware does improve read speed
marginally, so you might want to try that.
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