I've recently been setting up a sandbox ESXi environment with a VM running FreeNAS providing a volume which is connected as a datastore on the host via iSCSI.
I've created a VM on this datastore and the write performance is what I'd expect, around 280 MB/s (RAID 0 with 2 non-SSD ddrives). However using 'hdparm -tT' the read speeds are consistently around 450 kB/sec cached reads and 225 kB/sec buffered disk reads. Very slow!
I've created another iSCSI target on the same volume with freeNAS and I've connected to it within the virtual machine (ubuntu using open-iscsi) and I get reads of over 400 MB/s and writes around 320 MB/s, much quicker.
I'm at a loss as to why there is such a large difference when connected as a datastore with the esxi host or within the VM.
Anyone seen anything similar?
