MegaRAID Slow Performance

[Patrick Boutilier]

Chris Stark wrote:
> Hi,
> 
> I have a LSI MegaRAID i4 running in RAID 5 mode with 4 x 120 GB ATA 
> drives as my "/home" partition. The write performance is deplorably bad 
> (5 MB/s) but what's worse is that the system load shoots up to 15.0 or 
> even higher when I transfer any file that takes longer than a couple of 
> seconds. The system has quite a bit running on it (usually around 100 
> processes), but the load normally averages around 0.02 - 0.8 (when not 
> transerferring files).
> 
> I'm running FC3 and the system is a dual PIII 800 MHz, 1GB RAM, 20 GB OS 
> drive, and a Linksys Gigabit Ethernet card. The read performance isn't 
> too bad (~ 40 MB/s), and I know that RAID 5 brings _some_ performance 
> penalty to writes, but 5 MB/s seems ridiculous, especially considering 
> the high system load.
> 
> Also, for what it's worth, FC3 didn't detect the "megaraid" driver quite 
> right (it autoloaded the newer "megaraid_mbox" driver which doesn't 
> recognize the i4's logical drives -- I had to manually edit 
> /etc/modprobe.conf).
> 
> Any ideas how I can further troubleshoot this issue?
> 
Try adding elevator=deadline to your kernel line in /etc/grub.conf and 
reboot.