Volume & LUN reservation

[saranraj456]

Hi Buddies,

Is it feasible to reserve a space for LUN without having a reserved space for Volume?

Reserved space meant here is Space reservation,Fractional reservation & Volume guarantee.

Regards,
Saran

[chinchilla]

The configuration will work, but lun reservation won't be in effect.

If you want it to be in effect, you can set volume guarantee to 'file'

[radek_kubka]

Guys,

It is more complicated than that. Actually it is not recommended to set volume guarantee to 'file'.

If we create space reserved LUN within thinly provisioned volume (guarantee set to 'none'), the capacity equal to the size of the LUN will be taken from the containing volume and aggregate as well.

It used to be the case that fractional reserve settings were ignored completely for thin provisioned volumes (all behaved as for  fractional reserve set to 0%), but some bells are ringing it has changed somehow.

Regards,

Radek

[saranraj456]

Hi Radek,

Does the fractional reservation for LUN works in the scenario?

Thanks,

Saran

[radek_kubka]

Hi,

It actually does work:

http://now.netapp.com/NOW/knowledge/docs/ontap/rel801/html/ontap/bsag/GUID-596042AF-8E9C-4187-969C-633DFDD5A936.html

Fractional reserve can be used on the following types of volumes:

• Traditional volumes
• FlexVol volumes with a space guarantee of volume
• FlexVol volumes with a space guarantee of none You can only set fractional reserve for a volume with a space guarantee of none with Data ONTAP version 7.3.3 and later and version 8.0.1 and later. 

Note:  If the guarantee option for a FlexVol volume is set to none or volume, then fractional reserve for that volume can be set to the desired value. For the vast majority of configurations, you should set fractional reserve to zero when the guarantee option is set to none because it greatly simplifies space management. If the guarantee option for a FlexVol volume is set to file, then fractional reserve for that volume is set to 100 percent and is not adjustable.

But as they say - I wouldn't set FR to anything other than 0% for thinly provisioned volumes.

Regards,
Radek

[RAFAEL_GUEDES]

Hi Saran,

It depends on guarantee you put in your volume. If it is "none" and lun reservation is set to on for example, the lun space will be taken in the volume, but the volume won't reserve this space from the aggregate because lun reservations don't work with thin provisioned volumes. As chinchilla stated your volume guarantee should be set to "file" so this have the desired effect. When volume guarantee is file the fractional reserve is always set to 100, and it's not possible to change.

Since NetApp released vol auto grow and snap auto delete, we are encouraged to set FR to 0% and take advantage of this functionalities.

I suggest you take a look at this document http://media.netapp.com/documents/tr-3483.pdf.

It contains very useful information regarding your question.

[saranraj456]

Hi Guys,

i Just want to know in what ways or scenarios does the thin provision LUN will be used...?

with space guarantee for volume enabled ,space reservation for  LUN disabled..

Saran

[radek_kubka]

Hi Saran,

Firstly, it is hard to give a more thorough answer to your question than the TR-3483 mentioned above.

Secondly, your mileage may vary. I mean thin vs. thick provisioning is a classic example of a situation, where a number of different factors dictate what's right & what's wrong, with personal preference being often the most important one!

Regards,

Radek