Recommended vmfs block size

[vembustoregrid]

Hi All,

What is the recommended block size while creating a vmfs datastore, I am seeing 1MB to 8MB, shows large file require large block size. Does mean

that residing vmdk files ? Please share anybody having docs for recommended setup

Regards

Gopal

[AndreTheGiant]

There is no performance benefit on different block size.

But I suggest to standadize it and always you the same size for all your datastore.

For this reason 8 (the max) could be a reasonable size.

Andre

[VTsukanov]

:smileyplus: to post Andre

Also you can choose the block size considering the size of the storage. So, 1-2 TB storages correspond to blocks sized 4-8 MB, 0.5 - 1 TB storages - to blocks sized 1-2 MB.

[AWo]

Read this: http://www.yellow-bricks.com/2009/05/14/block-sizes-and-growing-your-vmfs/

It has some good background about the VMFS blocksize.

AWo

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[AndreTheGiant]

Also you can choose the block size considering the size of the storage. So, 1-2 TB storages correspond to blocks sized 4-8 MB, 0.5 - 1 TB storages - to blocks sized 1-2 MB.

This could be a good policy... but you can have some issues (for example with VDR or when you grow your volume and expand your vmdk).

For this reason now I prefer to use use always the max block size.

Andre

[VTsukanov]

Thank you, I didn't know such details about sub-block allocator

[vembustoregrid]

Ok... But as per this link article, even if i select 8mb blocksize, and i do incremental backup of vms ( by third party backup solution), does it backup

only kbs of blocks and not 8mb blocks .... thanks to sub-block allocator ?

Regards

Gopal

[AWo]

How do you want to do the backup?

With a standard backup agent running in the guest?

With an appropriate agent on the console, backing up the VMFS datastore?

....?

AWo

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[VTsukanov]

Normally we do with disks with disk space up to 256 GB and we use the third party backup, evidently we have not run across such issues.

In any case sub-block allocator makes your offer more preferable