Agreed, SSDs are simply not cost-effective at this point. 1.5TB costs something like $6000-6500 - no good.
I'm pretty sure the RAID processor would max out before the PCIe bus is saturated. A gen-1 8x PCIe slot provides 2GB/s bandwidth in both directions (wikipedia) and gen-2 should be double that. These are close to the rates of DDR2 memory and I doubt RAID cards are designed with these kind of numbers in mind.
Of course the filesystem is all important on a RAID system. I am using XFS. I have defragmented all my VMware images and I mount with "allocsize=512m" to cut down on new fragmentation.
With defragmented XFS image files, my VMware images are seeing excellent disk performance, almost as good as real disks.
XFS seems like the only choice for this application. I accidentally formatted a big RAID drive as ext3 once, it was so slow that I got totally disgusted about 2 minutes into using it.
Defragging makes a HUGE difference in throughput on these big files. I have no experience with SSDs, is defragging as important there? It seems like it wouldn't matter so much because there is no seek delay.
If you are going to defragment, you need to make sure the drives are not too full, or else the defragmentation process has no elbow room.
Last edited by frantaylor; 07-09-2009 at 01:47 PM.