Hi All,
I've been asked to comment and assist on a project team's build (which has already passed design stage and kit purchased etc).
For various reasons ESXi5.0.0 is to be utilised standalone to host a single VM running on local disk storage. The local storage is presented by a Fujitsu D2616 (almost entirely based on LSI SAS2108) with 4 7200rpm 500GB SAS disks. (THe HBA is not on the VMware HCL but the 2108 is)
The builders noticed immediately upon installing the guest OS that the performance was slower than they're used to and then found that attempting a snapshot of a smallish <40GB thin provisioned VM was taking 30 minutes to complete.
I've monitored ESXTOP during one of these snapshot attempts and found the write latency to be the obvious figure of concern - QAVG and KAVG stats are at 0ms with DAVG running between 20 and 30 for the duration of the write. They've now gone to rebuild the RAID settings on a number of the hosts in this particular cabinet to check (changing strip size, RAID levels, caching) etc with little or no change to this number. The next step is for them to ensure the RAID controller BIOS is at its latest version.
I don't have (m)any hosts with local datastore dependencies to compare and contrast with. In fact I look after busy iSCSI LUNs where DAVG spikes at 6ms when I run activities like snapshots which makes the latency here all the more intriguing.
Is there anyone else out there running a number of local datastores that could comment on the sort of performance they're obtaining or having to live with? Are we missing an obvious trick here somewhere? Cheers