Hi folks,
I've got a little bit of a frankenstein Dell server and I'm noticing that the storage is insanely slow. What makes it a non-standard Dell is that the original PERC H700 adapter has been removed, and in its place is a LSI 9217-8i controller with a pair of mirrored SSDs. The card was purchased as an 9207, but it was flashed with the compatible 9217 to give it the RAID firmware. There's also an LSI 9200-8e SAS controller in the system with nothing attached to it.
After noticing VM cloning being very slow, I tried from SSH in my /vmfs/volumes/<datastore> directory:
# time dd if=/dev/zero of=testfile bs=1M count=100
100+0 records in
100+0 records out
real 0m 7.59s
user 0m 0.23s
sys 0m 0.00s
That is, create a 100MB file on the SSD mirror. This takes almost 8 seconds! I think that comes out to about 13MB/sec for a sequential write. With a linux live CD, the same command takes a fraction of a second, and dd reports over 700MB/sec data transfer rate.
Just to make sure that my test is fair, I did the same sort of test on a similar server running ESXi, but with spinning-platter disks hung off of the H700:
# time dd if=/dev/zero of=testfile bs=1M count=100
100+0 records in
100+0 records out
real 0m 0.42s
user 0m 0.31s
sys 0m 0.00s
ESXi is the latest available 5.1 patch. The LSI driver has been updated as outlined here: http://adriank.org/how-to-update-mpt2sas-driver-on-esxi-5/
The LSI firmware has been flashed to match the updated version of the driver used by ESXi (19.0)
Why is the LSI SSD storage so slow? I wouldn't expect it to be because of the RAID-enabling flashing, as when booted to Linux the storage is amazingly fast.