VMDK size = VMFS Datastore size ??

[CCSL]

Is it possible to create a single vmdk file equal to the size of a vmfs datastore that it is created in or is there an element of overhead used by vCenter/ESXi.

I am using vSphere 4 and VMFS datastores are formatted as VMFS 3.33.

[rManic]

it is not possibe if you store the VM on the same datstore

Regards

manick

[rManic]

actual space required for a VMs is

disksize+memsize+vmx and other file sizes

[firestartah · Accepted solution]

You can't if it's the primary drive of a vm and the vm's configuration files etc are on the same datastore as the vm straight off the bat will need additional space for the amount of assigned memory. For a data drive this should be perfectly possible as there shouldn't be any additional files that will use up the space.

[CCSL]

Thanks for the responses. The datastore is just used for application data so no extra vm files. If I provision for example a 500Gb vmfs datastore the available space is always 'a bit' less than this. Does vCenter store some metadata in the datastore that takes up that space?

The reason I ask is that I am automating the creation of datastores and vm's with all additional disks required so I need to specify exact sizes in my powershell scripts.

[xingchan]

Why would you create a datastore per vm? If yoy create a datastore of 500GB and create an vmdk of almost 500GB vCenter keeps alerting you that you datastore is running out os space.

Default the swap file is stored in the same store. So you must reserve extra space for this also. If you create snapshots, you need extra space as wel.

[depping]

Why would you want to do it? If there is a specific need to isolate a workload just give it an RDM or at least give it some headroom for the vswp / logfiles / vmfs metadata.

Duncan (VCDX)

Available now on Amazon: vSphere 4.1 HA and DRS technical deepdive

[DCjay]

It should not be a problem.

I have seen customers using FC SAN for OS and SATA  SAN for data.

In this case you can have VMDK size almost equal to VMFS datastore size.

Jay