Thanks MKguy - I was really just looking for this sort of reality check.
The customer in this case is spoilt really without realising it giving that just about every other virtualised rig they run is backed by NetApp storage - latency for a similar task there is a mere blip and completes in seconds in many cases.
The concern was that the VM hasn't started doing anything yet other than booting into a new OS install and they wanted investigation before proceeding with application installs etc.
I'll check the registered driver as well as per your notes - much appreciated.
Edit to add:
Driver in question was this one https://my.vmware.com/web/vmware/details?downloadGroup=DT-ESXi50-LSI-2108-V534&productId=285
Checked on the host using 'vmkload_mod -s megaraid_sas |grep Version ' and determined we're at latest version. The kit is what it is - no batteries for the unit in this case which doubtless isn't helping - but they're happy now that this is just the performance they'll get in this configuration.
Cheers
Message was edited by: bobdhenderson