Decreasing LUN containg VMFS datastore..

[oweinmann]

Hi,

I ran into a serious problem today. One of our VMWare datastores ran out of disk space so I resized the Volume, then the LUN. I didn't pay attention to the maximum size Limit of 2TB for a VMFS datastore and received an error like:

Call "HostDatastoreSystem.QueryAvailableDisksForVmfs" for object "datastoreSystem-43668" on vCenter Server "" failed.

First I didn't even realize that this is related to the limitation of the datastore. And I started googling for the error and found nothing. What a suprise.

I resized the 1.86 TB LUN to 2.1 TB. All VM's are still running fine but now I wonder if I can decrease the size of the lun to 1.86TB without loosing or damaging the VMFS datastore?

Regards,

Oliver

[jjbitservices]

Did you resize the Datastore in VMware also?

If yes:

In my opinion the only thing you can do is:

Create a new 1.86TB lun and move all the VM's to the new LUN.

Finally remove the  2.1TB lun.

If you didn't resize / extend the datastore you can shrink the lun as long as the last datastore block is not changed

[oweinmann]

Hi I didn't increase the vmfs datastore as I was not able to do that. So shrinking the lun should not harm the datastore?

[arunchak]

If the VM's are important, then I think you should create a new 1.9 TB LUN, copy all the data and use this rather than taking the risk.

Once this is done you can try resizing the 2.1 TB lun

[MENCHEGO1]

What was the end result for you oweinmann?  I'm having the same issue as you had.

[macmillangm]

I agree with those that suggest a new LUN. If you shrink a lun you may not necessarily decrease its size by removing free blocks. You dont know where in the lun the free space is, so shrinking it to a smaller size may create more problems than it solves. I have had this same problem a few times and I always took the most cautious path by creating a new volume/lun and emptying the contents of the old before removing it entirely.