2011-12-08 01:15 AM
I would like to know the maximum I/O that I can expect with a FAS2040HA attached to a DS4243 (24x 450GB 15k RPM SAS drives).
I will run 20 VMs (vSphere 4.1) in NFS.
Thanks in advance for the feedback.
2011-12-08 02:51 AM
It's a bit "how long is a piece of string?" question...
What's the size of the IO? Is it random or sequential? What latency is acceptable?
As a rule of thumb, for short (4K or 8K) IO & reasonable latency (sub-20ms), each 'active' 15k spindle should deliver somewhere in the range of 180-220 IOPS.
'Active' spindles are your data drives, but not parity & hot spares, so as an example you may have following allocation (per each controller):
- 8 x data + 2x parity + 2x hot-spare
2011-12-13 11:20 AM
Radek is correct,
However this is a base number, system caching also contributes to the IOP profile as well. We have seen IOPs far in excess of what appears to be possible because the system has the data cached and is providing numbers higher than just the "spindle speed x count" would allow for.