The example below is not an actual configuration I am working with, but should get the point across. Here is my example of what I am referring to as a layer:
(Layer1) Hardware: Hardware RAID Controller
- -1TB Volume configured at 4K block size. (RAW?)
(Layer2) Hypervisor: ESXi Datastore
- -1TB from Raid Controller formatted with VMFS5 @ 1MB block size.
(Layer3) VM OS: Server 2008 R2 w/SQL
- -100GB Virtual HD using NTFS @ 4K block size for OS.
- -900GB Virtual HD configured using NTFS @ 64K block size to store SQL database.
It seems VMFS5 is limited to only having a 1MB block size. Would it be best if all or some of the block sizes matched on different layers, and why or why not? How do the different block sizes affect other layers and performance? Could you suggest better alternative or best practice for the above example configuration?
If a SAN were involved instead of a Hardware RAID controller on the host, would it be best to store the OS vmdk on the VMFS5 datastore and create a separate iSCSI LUN formatted at a 64K block size then attach it using the iSCSI initiator in the OS and format that at 64K. Do matching block sizes across layers increase performance or is it a best practice? Any help answering and/or explaining best practice is greatly appreciated.