ONTAP Discussions

Reduce size of LUN




For a temporarly reason I extend a volume and LUN size to 180Go (original 100Go). In my Windows 2008R2 Server I extend the volume too.

When I finish my operation I wanted decrease the size to return in the original state.


In Windows, I reduce the volume to 100Go, in the disk manager it is ok. The partition doing 100Go and see 80Go of not allocated space.

In NetApp OnCommand System Manager the free space of the LUN stay at 25Go... why ??? Too, in my 100Go Windows partition I have 48Go free.


Finally I cannot reduce the lun size because System Manager see only 25Go of available space Man Frustrated



Can you explain and help me this situation ?








Hello Jules


welcome to communites..


few questions...

1.Did you write into the lun? (write and delete operations done?)

2.Does your volume has a snapshot enabled on it.

3.Do you see snapshots on that volume?

4.Are you disconnecting the lun and then resizing it?


For online resizing the lun on windows i would use the Snapdrive tool.





Hi Jules,

The key thing to make much of this easier in future is to use NetApp snapdrive to manage tour windows luns. Snapdrive manages many if the things you are seeing here.

There is a disconnect between what windows sees and what the underlying ONTAP lun/volune sees without snapdrive.

What is likely here you extended the LUN probably used around 125gb, deleted some files and the shrunk the LUN in Windows, however in reality what happens is those blocks are only ever marked for deleting. At an ONTAP block level these blocks still have data in them.

The way to fix this is a space reclaim, which is something snapdrive will allow you to do, this will tell ONTAP that those blocks can be freed this will then allow you to reduce the LUN. Snapdrive helps with all that, strongly suggest you install it and will greatly simplify you LUN management.

Hope this helps.