Thank you for the response Marcelo,
I have only obviously scratched the surface with ESXi5, I didn’t know the esxtop command was so comprehensive.
Following the KB article I can esxtop and monitored performance on a per LUN basis focusing on the Synology iSCSI LUN. To perform the test I took a snapshot of a VM while monitoring the changes. As per the screenshot (https://dl.dropboxusercontent.com/u/1428230/ESXi5.1/SnapshotLUN.jpg ) I’m getting around 13 MBWRT/s – 20 MBWRT/s. The VM size is 17GB in size but 40GB thin provisioned.
Yes, The Synology is supported ESXi as per: http://partnerweb.vmware.com/comp_guide2/detail.php?deviceCategory=san&productid=20600&vcl=true
As you suspected there looks to be a ton of errors/warnings in vmkernel.og which relate the iSCSI mount point (naa.6001405b53e1852d3615d34f2dabb2d5"). In fact there are so many I’m at a bit of a loss of where to start first. Looking at the iSCSI KB articles there are many paths to follow. Hoping someone with some more experience can skim over the log and suggest a first angle of attack. I have uploaded a large chunk of the log here: http://pastebin.com/i0GSTUkC
Thanks,
Adam