topic Compression in ONTAP Discussions

Compression

asharmaA — Wed, 04 Jun 2025 13:02:14 GMT

Hi Team

We have a snapmirror relationship between vfiler vols. mounted the source volume on windows server &copied the files in the zip. The snapmirror is scheduled to run every 2 hours.

I had 2.5 TB of files. I added these files to multiple compressed (.zip) files and the size of zip files after compression was around 500 GB. I expected the size of the volume/vfiler to drop by 2 TB after the next snapmirror transfer is complete.

Does NetApp storage not recognize when a file has been compressed. However mounting the volume on windows server is showing the size of ZIP file is decreased by 2 TB. Is this an expected behavior?

Thanks

Re: Compression

GidonMarcus — Sat, 15 Dec 2018 15:29:17 GMT

Volume size include snapshots as well. if you still have snapshots containing the files in the original form. you need to delete these snapshot to recover the space.

You also didn't mention what protocol and configuration your volume is mounted to windows.

if it's in a block base form, the file system(s) that manages the partition(s) also manages the empty blocks. and it might keep them full with garbage or zeroes. recent OS and Hypervisors (in case they have their own files system to host virtual disks) could tell ONTAP to mark a block as obsolete by sending an SCSI UNMAP command. if they do not - ONTAP assumes it's in used by the client regardless for the content (including garbage and zeros)

Gidi

Re: Compression

Asharma — Mon, 17 Dec 2018 15:48:36 GMT

Hi Gidi

It is a cifs volume inside a vfiler. I followed the below steps:-

1. I mapped the share present inside the volume on to a windows server as it is a CIFS NAS volume.

2. I had 2.5 TB of files. I added these files to multiple compressed (.zip) files and the size of zip files after compression was around 500 GB. I expected the size of the volume/vfiler to drop by 2 TB after the next snapmirror transfer is complete.

3. The snapmirror is configured to run every 2 hours. Therefore, once the snapmirror transfer is complete the size should have decreases by 2 TB.

4. The volume has deduplication enabled.

Please suggest if the zip file is showing me 500 GB after compression why does the size of volume is still the same.