topic Re: strange issue when resize volume in ONTAP Discussions

strange issue when resize volume

fcorfdir — Thu, 05 Jun 2025 07:14:50 GMT

So I have a Volumes with sis on from 1.2 TB, on this volumes I have a vmware iScsi lun of 1 TB. I Want to resize the lun to 1.5 TB.

On volumes manage my lun have available 0 B, Used 100%, total 1.2 TB. So I go to my volume and next to resize storage wizard. I Change the volumes size to 1.6 TB all working good but when I Go back to volumes manage I see that the volume have been immediately consume before that I have the time to resize my lun.

so how can I reclaim this space ?

here are some picture snapshot

Re: strange issue when resize volume

lwei — Sun, 02 May 2010 05:09:38 GMT

What's your volume's snap reserve? You can consider reduce that or reduce Fractional Reserve. -Wei

Re: strange issue when resize volume

fcorfdir — Sun, 02 May 2010 21:39:09 GMT

So I need to do a vol

options vmwarev1 fractional_reserve 0

and my space use will be reduce ?

Re: strange issue when resize volume

lwei — Mon, 03 May 2010 03:35:16 GMT

Can you do a "lun show"? How many LUNs are in that volume? Looks like the volume's size is 2TB; Snap Reserve maybe 20%. That leads to 1.6TB Total Capacity.

Thanks,

Wei

Re: strange issue when resize volume

fcorfdir — Mon, 03 May 2010 05:08:07 GMT

juste one lun for the moment

sanv1a> lun show

/vol/vmwarev1/vmfs1 1024.0g (1099494850560) (r/w, online, mapped)

sanv1a> vol options vmwarev1

nosnap=off, nosnapdir=off, minra=off, no_atime_update=off, nvfail=off,

ignore_inconsistent=off, snapmirrored=off, create_ucode=on,

convert_ucode=off, maxdirsize=18350, schedsnapname=ordinal,

fs_size_fixed=off, compression=off, guarantee=volume, svo_enable=off,

svo_checksum=off, svo_allow_rman=off, svo_reject_errors=off,

no_i2p=off, fractional_reserve=100, extent=off, try_first=volume_grow,

read_realloc=off, snapshot_clone_dependency=off

Re: strange issue when resize volume

scottgelb — Mon, 03 May 2010 05:22:46 GMT

When we run SIS on volumes with LUNs, you don't see the space savings when lun reservation is set. Does "lun show -v" show reservation is set on the lun? This has to do with the lun reserving space in the volume which is separate from fractional reserve which is snapshot space reserved in the volume. You could have a fully provisioned lun with no space reserve for example. The issue you are having looks like a snapshot was created and is reserving the space that looks like it should be available.

When running dedup, turn the lun reserve off "lun set reservation" then the dedup space will go back to the volume. To take it further, you can turn off volume reservation and the dedup space will go back to the aggregate. The use of this depends on where you want to see dedup savings...either back to the volume for other luns in that volume or to the aggregate for use by other volumes in that aggregate. The key thing is to monitor usage so you don't run out of space and also look at snapshot autodelete and/or volume autogrow.

Re: strange issue when resize volume

saranraj456 — Sat, 29 Oct 2011 09:28:53 GMT

Just set the Fractional reserve to zero you would get back your volume size.

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Saran

Re: strange issue when resize volume

shashidhargc — Thu, 07 Mar 2013 11:44:06 GMT

This is only because fractional reserve is set to 100. What happens when FR is set to 100 on a deduplicated volume is Any blocks freed through deduplication are allocated to the fractional reserve area. This configuration ensures that overwrite to the LUN should never fail even if it is overwritten entirely. And hence your volume shows 100% used.

Setting FR to 0 "forces" all the freed blocks to the volume free pool and no blocks are set aside for fractional reserve. Thus your volume will only consume space for the only actual deduplicated data.