Thin and Thick Volume show different allow space

[areti]

I have a FAS2750 ONTAP 9.8 P3.

When I create a new Volume and LUN for vmware in the ONTAP System manager wizard, the Volume and LUN are thin provisioned by default.

For example, LUN 10 Gb and vol 10.2 Gb.

At the same time, in the ONTAP System manager in the volume size indicators, the actually occupied size is shown (file_1 attach)

If you change the Volume and LUN properties to Thick Provisioned, then the Volume shows that it is fully occupied even if the LUN is empty (file_2 attach)

Is this right?

On the other fas2750 ONTAP 9.7 P3 if the Volume and the LUN are Thick Provisioned, then the Volume always shows only the space actually occupied by the data, even if the LUN is the size of the entire Volume, example Volume 51 Gb and LUN 50 Gb (file_3 attach)

Why is that?

[aladd · Accepted solution]

This can make a difference depending on your configuration for fractional reserve and space reservation in the volume and LUN.

A thick provisioned LUN should typically show the full size of the LUN, fractional reserve will preserve additional space for write guarantees.

REF:

Fractional reserve:

https://docs.netapp.com/ontap-9/index.jsp?topic=%2Fcom.netapp.doc.dot-cm-vsmg%2FGUID-596042AF-8E9C-4187-969C-633DFDD5A936.html

space reservation:

https://docs.netapp.com/ontap-9/index.jsp?topic=%2Fcom.netapp.doc.onc-sm-help-900%2FGUID-9E67E4A4-DF81-4941-9C67-0EB732C3014F.html

Deduplication can also make a difference, but most likely are in relation to the settings of the above.