VMFS Block Size Question

[Brandon7a]

I created a 600GB LUN. I then go to the ESX host that contains the datastore - Configuration tab - Storage - Select the Datastore.

Why does it say my 600GB LUN is a block size of 8? When I create a 600GB LUN, shouldn't it be a block size of 4?

It says my VMFS file system is 3.46.

I'm running vCenter 5.0 with ESXi 4.1

Thanks

[a_p_]

The block size is not related to the size of the datastore. It defines the maximum size of a file on the datatore (e.g. a virtual disk file - .vmdk). You can create/format the datastore with every possible block size as long as it supports the maximum virtual disk size you need. With VMFS-5 this is history and the unified block size for all file sizes is 1MB.

André

PS: for block size vs. file size, see http://kb.vmware.com/kb/1012384

[Brandon7a]

I guess my question is how did the block size become 8MB? When I created the LUN, it did not ask me for the block size.

[a_p_]

When I created the LUN, it did not ask me for the block size.

If a datastore is created using the wizard, you will have to select the block size on - I think - the second screen. I'm not aware of a way to create a datastore with a block size <> 1MB without manually specifying it.

André

[Brandon7a]

I created the datastore through my EMC VNXe 3100 interface. Should I have created the datastore through the virtural client?

[a_p_ · Accepted solution]

I created the datastore through my EMC VNXe 3100 interface

I' don't know this interface, but this might have created the datastore with an 8MB block size. Anyway, there's basically nothing wrong with the 8MB block size. You won't have any performance penalties compared to another block size.

André

[Brandon7a]

Thank you for your answers. One last question. You mentioned in vSphere 5 that all block sizes will be 1 MB. Will this change automatically on my current datastores when I upgrade?

[a_p_]

No, the block size of an existing datastore will remain the same when you upgrade it to VMFS-5. New datastores will be created with the unified 1MB block size.

Upgrading the datastores is a manual process which can/should be done after all ESXi hosts accessing the datastore are running on ESXi 5.0

André

[a_p_]

Maybe interesting to read: http://blogs.vmware.com/vsphere/2011/07/new-vsphere-50-storage-features-part-1-vmfs-5.html

André

[mcowger]

Note that theres still no real benefit to choosing anything besides 8MB, so I wouldn't worry about it.  You get all the benefits of the large block size, and no costs (theres even a small theoretical performance improvement).