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Extending VMWARE VMFS datastore

Posted on 2008-11-15
Medium Priority
Last Modified: 2013-11-14
We have a VMWARE ESX Server 3.5 up and running.
Because of budget restrictions we only have local SAS harddisks.
The SAS harddisks are configured  as one RAID5 array.
We now extended the RAID5 array by adding two more physical disks.

Now we also would like to extend the VMFS datastore.
When I choose "Add/Extend" I get the following warning:
"The current disk layout will be destroyed. All file systems and data will be lost permanently." (see screenshot attached)

Before I proceed I would like to answer the following question:
- Will all our VMDK virtual machine images be destroyed?
- Isn't it possible to just extend the datastore without loosing all data?
- What is the fastest way to backup all our VMDKs? (if required)
- Any other thougts an this issue?

One more annotation: The ESX server itself is installed on another RAID1 volume.
This means, that the RAID5 voulme is "only" used for VMDKs.

Thanks for your advise!
Volker :-)

Question by:kurthv
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LVL 18

Accepted Solution

larstr earned 1500 total points
ID: 22970346
I'm sorry, but you can't extend a VMFS datastore just like that. You can add several extents to a datastore, but it's not really something I would recommend.

The best solution would be to build a new datastore of the required size and move your VMs over there. For a standalone server with local storage setup that might mean that you must backup your VMs and restore them again.

Note also that RAID 1 or RAID 1+0 is normally better for hosting VMs than RAID5 since it will give you much better performance for a mixed workload.

The easiest way to backup/restore your VMs is probably to use esxpress or similar.


Author Comment

ID: 22970595
This would mean, if I click on "Next", then all data would be destroyed, right?
LVL 18

Expert Comment

ID: 22970634
> This would mean, if I click on "Next", then all data would be destroyed, right?

That's correct.

Author Comment

ID: 22971992
Hi Lars,

I did backup all the VMDKs (using esXpress).
Then I performed the "Add/Extend" operation.
I was expecting to loose all my VMDKs, but they are still there.
See the attached screenshot...

So the warning message was wrong!

Best regards,
Volker :-)

LVL 18

Expert Comment

ID: 22973835
Are you adding an extent now? If you do that, beware of the limitations. Also see: http://www.vmware.com/pdf/vmfs-best-practices-wp.pdf

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