topic Re: Increasing LUN Size in ONTAP Hardware

Increasing LUN Size

GUVNIJJAR — Thu, 05 Jun 2025 06:27:15 GMT

I have a lun with size 400gb, on a volume which is ITB, the lun has FR set to 100 %.

I want to increase the size of the lun, so do i use the below command:

lun resize <lun path> +50g................so i want to increase by 50gb. So is it ok to use the + increment. Also is it better to state the new value size:

lun resize <lun path> 450g

Does it make a difference what command you use. Does it take long to increase.

Also does the FR increase as well in size when the lun size increases as well.

Thanks

Re: Increasing LUN Size

aborzenkov — Thu, 17 May 2012 10:10:31 GMT

It does not make any difference whether you use incremental or absolute form.

Fractional reserve applies to currently occupied LUN size, so reserved space will not increase initially after increasing LUN size (because no space is actually consumed). But of course if host later writes into this space, fractional reserve will increase.

Re: Increasing LUN Size

radek_kubka — Thu, 17 May 2012 10:17:25 GMT

Fractional reserve applies to currently occupied LUN size, so reserved space will not increase initially after increasing LUN size (because no space is actually consumed)

Don't want to be too picky , but are you sure about this? I was always under impression, that FR takes care about declared size of the LUN, not how much space is actually used.

Regards,

Radek

Re: Increasing LUN Size

aborzenkov — Thu, 17 May 2012 11:40:11 GMT

Yes, I am sure. FR is by definition space reserved for overwrites, which means - amount of space currently occupied. If you have fully thick provisioned configuration, LUN reservation takes care of allocated size and fractional reserve takes care of currently occupied size.

Re: Increasing LUN Size

radek_kubka — Thu, 17 May 2012 11:56:30 GMT

Yep, you are 100% correct - now I remember how I used FR reserved values to figure out how much data has been written to a space reserved LUN.