topic Re: Lun and volume free space difference in ONTAP Discussions

Lun and volume free space difference

cit_fas2050 — Thu, 20 Apr 2017 10:14:57 GMT

Dear all,

My system is FAS 2552 in c-mode 8.3.2

For my vSphere cluster I have 4 1TB LUNs in VMFS. Each LUN is in one think provisionning volume of 1.2TB. Deduplication is enable

I don't understand why I have more free space on my LUNs instead of my volumes ?

For example : my LUN1 have 380GB free space but volume have only 151GB free space. This night I move many data in a virtual machine (approximately 200GB), my VMs are in think provisionning. This morning my datastore is down When I see the free space, the LUN is ok but my volume is full. How it is possible my volume was full while my LUN is smaller than my volume ans not full ?

Thanks for your explanations

Regards

Re: Lun and volume free space difference

nicholsongc — Thu, 20 Apr 2017 16:02:16 GMT

I'm having difficulty following the wording of your question. Are you trying to say that these are THIN or THICK provisioned volumes?

Also - are you going by the vCenter/Host reporting of LUN space or by Netapp/Sys Mgr? I've learned that you should ALWAYS go by the HOST's perspective when it comes to determining the utilization of LUNs... this is true of ANY storage vendor.

Re: Lun and volume free space difference

cit_fas2050 — Fri, 21 Apr 2017 07:16:20 GMT

Sorry for my English

My volumes are thin. The problem is not the free space on my LUN but on my volume. How can I no longer have free space in my volume while on my LUN there are still ? My LUN is smaller than my volume...

The view is in NetApp Data Ontap

Regards

Re: Lun and volume free space difference

cit_fas2050 — Mon, 24 Apr 2017 13:18:16 GMT

Nobody to answer me ?

Re: Lun and volume free space difference

alexj — Mon, 24 Apr 2017 15:52:13 GMT

Sounds to me like you have snapshots enabled without knowing it and/or a lack of fractional reserve. You need to leave enough space free in the volume to account for overwrites and snapshots.

Fractional reserve info: https://library.netapp.com/ecmdocs/ECMP1393894/html/GUID-596042AF-8E9C-4187-969C-633DFDD5A936.html

Re: Lun and volume free space difference

mduraphe72 — Tue, 02 Jun 2020 09:39:08 GMT

What is standard difference between Total LUN Space and Total Volume Space?

Why there should be space difference between Volume and LUN? What is purpose?

Re: Lun and volume free space difference

Mjizzini — Wed, 03 Jun 2020 11:54:21 GMT

LUN is a large file inside the volume. You can have multiple LUNs in the sam volume.

Total Volume size= data space + space used by Snapshot copies or the Snapshot reserve (whichever is greater).

Configuring volumes to automatically grow and shrink their size

https://docs.netapp.com/ontap-9/topic/com.netapp.doc.dot-cm-vsmg/GUID-ECE453FE-D158-4BDA-9851-6B8780474E11.html

Re: Lun and volume free space difference

Mjizzini — Wed, 03 Jun 2020 12:07:10 GMT

LUN is a large file inside the volume. You can have multiple LUNs in the same volume.

Total Volume size= data space + Snapshot reserve .

Note that, if the snapshot copies grow to be bigger than the Snapshot reserve size, the volume data space will be used for extra snapshot space.

Configuring volumes to automatically grow and shrink their size

https://docs.netapp.com/ontap-9/topic/com.netapp.doc.dot-cm-vsmg/GUID-ECE453FE-D158-4BDA-9851-6B8780474E11.html