U320 RAID 0 performance as array size grows
Posted on 2003-10-30
I have a dual channel LSI Logic PCI-X 64bit/133mhz U320 scsi adapter. I'm running RAID 0. As I added drives to the array I noticed that the performance increase leveled off quickly. I'm using fujitsu U320 10k drives.
Below is a quick summary of sequential reads in MB/sec of the array:
1 - 67
2 - 120
3 - 170
4 - 190
6 - 225
8 - 245
Array sizes 1, 2 and 3 were on 1 channel. Array sizes 4, 6 and 8 were spread accross 2 channels.
My main question is this: is this typical?
I'm new to raid so I wsn't sure what to expect. I dont know if I have a problem or if this is simply the real world limits of U320. I knew I wouldnt get 320 MB/sec per channel but I was surprised to get only 245 MB/sec off dual 320 MB channels.
If this is typical, then what is the bottleneck here? Is the scsi bus getting saturated? Or is it the SCSI controller itself reaching its limit?