topic FlexVol volume nearly full in ONTAP Discussions

FlexVol volume nearly full

Jerry2 — Wed, 04 Jun 2025 10:02:24 GMT

Hi all,

could you please help me to understand following situation.

We have FlexVol volume that is 1TB in size and it is nearly full. The snapshot reserve is 5% and it is utilized at 120.% We have enabled to automatically delete the oldest snapshot copies with a volume threshold trigger. How much disk space will be available, if there is only default settings?

According to https://kb.netapp.com/Advice_and_Troubleshooting/Data_Storage_Software/ONTAP_OS/How_to_use_Snapshot_Autodelete - Snapshots are deleted, one at a time, until the used volume space reaches the value specified by "Target Free Space." The default for "Target Free Space" is 20% free space or 80% utilized

I guess, immediatelly when the trigger value is reached, it should be made available 80% and it means 80% from 1TB, which is 800GB. Am I right?

Re: FlexVol volume nearly full

Mjizzini — Tue, 12 Apr 2022 08:16:05 GMT

It will be true if you set the trigger to "snap_reserve" and set the reserve to 20%.

Depending on what is selected in the "Trigger" option, Snapshot Autodelete will automatically delete a snapshot when, either the volume space utilized, or the snapshot reserve reaches a threshold capacity specified below.

When the "volume" option is selected, Snapshot Autodelete will begin deleting snapshots when the volume reaches the threshold capacity AND the volume space reserved for snapshots is exceeded. If the space reserved for snapshots is zero, then exceeding the reserved snapshot space is always true and only the volume capacity threshold is used. The capacity threshold used is determined by the the size of the volume as follows:

If volume size is equal to or greater than 1 TB, the threshold is 98%.

When the "snap_reserve" option is selected, Snapshot Autodelete triggers automatic deletion of snapshots when the space reserved for snapshots reaches the value assigned the volume in "Space Reserved for Snapshot Copies" (see manual entry for volume show.)

Re: FlexVol volume nearly full

Jerry2 — Tue, 12 Apr 2022 13:44:24 GMT

Hi @Mjizzini, thank you so much for you input!

Then, I have last concern. In the documentation it is said "When the "snap_reserve" option is selected, Snapshot Autodelete triggers automatic deletion of snapshots when the space reserved for snapshots reaches the value assigned the volume in "Space Reserved for Snapshot Copies""

Then, how many snapshots will be deleted if there is "snap_reserve" set the reserve to 20%? Does it mean that ALL snapshots will be deleted until the volume takes 80% of their capacity?

Re: FlexVol volume nearly full

DarrenJ — Wed, 13 Apr 2022 04:32:52 GMT

Per the KB linked, it will start with the oldest snapshot first (by default) and delete them one by one until you are back under 80% space used within the volume. This could potentially delete ALL snapshots, depending on the circumstances, but by design it can if that's what's required to get below the 80% space used.

Re: FlexVol volume nearly full

Jerry2 — Wed, 13 Apr 2022 11:14:15 GMT

Hi @DarrenJ, thank you very much for the clarification!