topic Ontap 7 - Provisioned LUN in SM shows less free space than Server mapped drive. in ONTAP Discussions

Ontap 7 - Provisioned LUN in SM shows less free space than Server mapped drive.

PraveenPP — Wed, 04 Jun 2025 20:14:00 GMT

Some of the reserved space is reclaimed after the completion of the command, “SIS”

But still we are facing a space mismatch with LUN and mapped drive in system.

I am attaching the screen shots of Aggr, Volume and Drive with details.

I have a few questions,

Does that mean even if I empty 1 TB from LUNs, the NETAPP will never update the free space? What will happen when NETAPP see LUNs 100% full while it actually have more than 500GB empty space? Will the LUN goes offline? Will installing SNAPDRIVE help? currently it is not installed on Share Server.
Because the Volume is thick? So If I changed the volume to thin, NETAPP will see the correct available space reflected on the LUN?
What caused the dedup meta database to explode in size, is there a knowledge base detailing the reasons that caused this to happen? Wasn’t storage efficiency supposed to help storage by reducing used space?

I am attaching the screen shots of Aggr, Volume and Drive with details.

Re: Ontap 7 - Provisioned LUN in SM shows less free space than Server mapped drive.

NAYABSK — Mon, 27 Jun 2016 02:40:32 GMT

Hi Praveen,

This is a usual behaviour of Ontap

Long back i had the same confusion seen some volumes shown threshold reached 70 % but in my windows box showing plenty of free space available. I was wondered what is happening to my storage and i found the reason why .If you delete a load of data from the client-side (eg NTFS) the client marks the blocks as free, as opposed to physically zero'ing out the data, right? Down at the storage level WAFL has no way to know these blocks have been deleted, so when you write more data to the LUN it will consume new blocks in the volume. Typically, as a LUN ages, you will find the NetApp side will show the LUN at, or close to 100% full, but the clients filesystem may still have plenty of space. This is by design, and often not a problem - although it looks a bit odd at first. Check out Snapdrive's Space Reclaimer feature if using Windows - this will reclaim those free blocks at the WAFL end if required.

Tool to reclaim space :- Snapdrive

Automatic Reclaim at the Ontap level is possible from Cluster Mode 8.2 or later releases.

Thanks,

Nayab

**** If my answer helped to solve the issue, Please mark it as solution so that it will be helpful to others****

Re: Ontap 7 - Provisioned LUN in SM shows less free space than Server mapped drive.

PraveenPP — Mon, 27 Jun 2016 13:36:52 GMT

Dear Nayab,

Thank you so much for the help.

Please to update you that your answer helped me to explain the solution to the Customer.

Regards,

Praveen

Re: Ontap 7 - Provisioned LUN in SM shows less free space than Server mapped drive.

NAYABSK — Mon, 27 Jun 2016 13:44:12 GMT

Hi Praveen,

Glad to know that it helped you 🙂

*****Can help me to mark my reply as answer so that it will help others who are facing the same issue as yours****

Thanks,

Nayab