Hello guys,

I have 2 VMWARE Servers in DAG - both with mailbox role.

Which storage type is better for databases and logs for higher availability- VMDK or RDM?

I did not find official document which strictly recommends which one?!

I would only use RDM is the drives exceed 2TB. Otherwise, there is really no difference performance wise.

Hi there

There is actually no performance difference(+/- 1%) between the 2, you can check VMware Blogs for tests they ran. 

RDM disks used for microsoft fail over clustering these days. For exchange , go with VMDK.

Some Disadvantages of RDM Disks:

• You wont have metrics for these disks in VMware vRealize Operations, so you should monitor them on your storage device.
• Your Management loadwill increase as for vMotion and HA considerations.

Hope This helps.

Farhad

Agreed.  VMDKs is the least complex way to go