Data Backup and Recovery

Downsizing one LUN to give space to another




I have two LUNS on the same filer. They are marked as disks on a file server. Both LUNs have a maximum size of 1.9 TB.


One disk is almost full, while the other has about 600GB available space. Can I by using SnapDrive downsize the one with available space, and then add this space to the other?


Could it really be that simple? Also, what are the pitfalls? Can I do this while the server is running without any interuptions to users?


Fairly new to NetApp, so wanted to make sure I don't **bleep** anything up 🙂


Any help or advice would be greatly appreciated.


Kind Regards






Yes, you can shrink LUNs using SnapDrive and it is an online operation.


However do you know your underlying volume layout? Each LUN resides inside a volume, so if you have two LUNs, they can be in the same volume, or in different volumes. If the latter is true, then shrinking LUN1 won't release any space for LUN2, if you know what I mean - you may need to amend volume sizes accordingly as well.





Hi Radek and thanks for your reply.


The two LUNs sit under the same Volume: /vol/ESX_DS_FILE, so this means it should be very straight forward?


Downsize FILE_Filestore2 and I can then use that space to extend FILE_Filestore?


On the virtual machine, will I need to do anything or should it just automatically reflect new space?


Thanks again.


EDIT: my bad, using the SnapDrive on the virtual machine of course to resize the lun..what will I need to do on the OnCommand side of things?


Your initial post didn't mention anything about virtualised environment and it is still not clear how the LUNs are presented to the VM - RDMs? VMDKs? Software iSCSI?


Either way, if you can see the LUNs via SnapDrive from inside the guest [EDIT: and they are not VMDKs], then you should be able to resize them.



SnapDriver also supports VMDK on datastore; and it definitely cannot resize datastore itself.


Note that VMFS cannot be reduced in size; so the only possibility to actually reduce space consumption is either use Storage vMotion to move data to new, smaller, datastore or enable thin provisioning and perform space reclamation.


@aborzenkov wrote:

SnapDriver also supports VMDK on datastore; and it definitely cannot resize datastore itself.

Yes, sure thing - SnapDrive won't change VMDK size.


LUN resize 1.JPGLUN resize 1.JPG



So this is from the VM, as you can see there are two LUNs, residing under the same volume.

They have their own vmdk, so what you are saying is that even if I downsize LUN2 I can't allocate the spce to LUN1? The vmdks will stay the same size, what if I use Space Reclaimer after downsizing?


Thanks again, I am new at this so I might be getting this all wrong 🙂