Quick post for now, I’ll come back later and update it with more details after I read it 🙂
When doing any install of Exchange I always insist on running JetStress to make sure the storage is working as expected. About half the time it is not, most of these are where the client has a new iSCSI infrastructure setup. There are many factors that can affect performance with iSCSI, but the most common that I’ve seen are old\incorrect drivers and incorrect network configurations.
So always run JetStress to make sure the storage is delivering the IOPS needed and the I/O latency is below 20ms on average and has no peaks over 50ms. With JetStress 2010 you had to de-tune JetStress manually so it only generated a similar number of IOPS as what the Exchange Storage Calculator recommends.