Raid1 read performance.

[Peter Mueller]

> 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.

Regards,

P