RAID 5 mystery
In one of my servers, there is a 3-drive RAID 5 built on a LSI 320-1 U320 SCSI Raid Controller. There are 3 36GB, 10Krpm, U320 drives on it. I had all of the caching, read-ahead, etc, disabled in the interest of data integrity.
While on the phone with the LSI technician, we ran 10MB FTP benchmarks on the array, getting a max read speed of about 72,000KBs (72MBs), which with these settings is reasonable for a RAID 5 with only 3 drives. But, the write speeds are like 6,000KBs (6MBs)!!
I enabled the I/O caching,and the read-ahead, and the read speeds rose to 110,000KBs. Nice, but there was no change to the write speeds at all.
The LSI tech acknowledged that the write speeds are 1/3 to 1/2 of what they should be (even with the drives set to write-thu, again, for data integrity), but was unable to offer any assistance.
Any information that sheds light on this situation would be greatly apprediated!
Thank you for your time.