topic Re: LUN bigger than volume in ONTAP Discussions

LUN bigger than volume

AlexandreOliveira — Wed, 04 Jun 2025 11:02:04 GMT

Hello, I am seeing this very strange behavior:

# df output

/vol/vol_SQL1_MS1_Data_1/ 3328599656 3180880684 147718972 96% /vol/vol_SQL1_MS1_Data_1/
/vol/vol_SQL1_MS1_Data_1/.snapshot 0 0 0 0% /vol/vol_SQL1_MS1_Data_1/.snapshot

#lun output

LUN name: /vol/vol_SQL1_MS1_Data_1/SQL1_MS1_SQLData_1.lun

Lun size : 5046636994560

How can I have a 4.7TB LUN inside a 3.1TB volume?

Some points to consider:
- Volume has space guarantee set to volume.
- LUN has space reservation disable
- LUNs expansions are managed via SnapDrive on Windows

Thanks!

Re: LUN bigger than volume

aborzenkov — Tue, 07 Jul 2020 14:46:11 GMT

@AlexandreOliveira wrote:

How can I have a 4.7TB LUN inside a 3.1TB volume?

You answered it yourself:

@AlexandreOliveira wrote:

- LUN has space reservation disable

Re: LUN bigger than volume

AlexandreOliveira — Tue, 07 Jul 2020 14:51:39 GMT

But shouldn´t the LUN size be limited to the volume size?

Re: LUN bigger than volume

keitha — Wed, 08 Jul 2020 14:18:49 GMT

No. You can certainly have a LUN much larger than the volume. Think of the LUN as the presentation to the outside work. How much space do you want the host to see. The volume then is how much space do you think the data is actually going to take. This way unused space in the LUN and duplicate and compressible data is not consuming space in the volume. You can of course change the volume size up or down on the fly without the host being aware.

Re: LUN bigger than volume

Mjizzini — Fri, 10 Jul 2020 03:59:56 GMT

You set up is valid. Note that the LUN will go offline when the volume will be full.

You can have a bigger volume with no space guaranty (thin prevision) or Make sure you have volume autosize set.

volume autosize

Re: LUN bigger than volume

AlexandreOliveira — Fri, 10 Jul 2020 12:57:08 GMT

Just a correction, the LUN will not go offline when the volume gets full. It will probably go offline when the aggregate goes full.