Data Backup and Recovery Discussions

shrinking a LUN


storage: FAS31240

version :

volume: flexible

I am looking to shrink a lun, but when trying to do so with snap manager, it is greyed out.... Why is that ?...




Hi David,

Normally LUN shrink is a rare operation and it makes sense to shrink a LUN when a large part of that LUN is unused over a period of time. Probably Snap Manager treats that LUN as a whole data file from application point of view; hence not allowing doing such operation.

Can you please share with us about the use case for LUN shrinking?




If I'm not mistaken, LUN shrinking is only supported with Windows 2008.


As far as I know, Windows Longhorn was supposed to provide this LUN

shrink facility. We need to check this.

But if I understand properly, SDW 5.0 has a feature to reclaim space

from unused file system from ONTAP 7.2.1 onwards. This might work as

virtual LUN shrinking facility.




There are two separate features:

Shrinking -- only available with Windows 2008.  This will let you actually shrink the size of the lun

Reclaim -- available with DOT 7.2.1+, will let you free up FAS blocks based on NTFS block usage.   So if you wrote a 50 GB file in NTFS, then deleted it, you could reclaim the 50GB that ONTAP used within the lun.


You could try the LUN resize command from the cli also...... I would be very cautious of this though. I have done it in the lab.... but would I do it with live data... NO

Create a smaller lun if your heart is set on doing it and move the data into the smaller lun.


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