MegaRAID Slow Performance

Chris Stark cstark at hawaii.edu
Thu Feb 3 23:48:29 UTC 2005


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?

-- 
Chris Stark
Musician, Linux User, Grad Student
http://chrisstark.com




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