snapshot size is reported to be very large whereas it should be very small

[BelaAtCU]

Hi All,

I was moving about 8TB data into a Ontap Volume. The snapshots were  already enabled when the transfer took place. I expected to have very small size snapshots because we are moving data to the volume and do not delete any.  My understanding is that snapshots grow in size when data/files are being deleted.

In the snapshot list I bolded some of the sizes that stand out:

Daily_evening.2021-09-29_2235 67.63MB 0% 0%
Daily_evening.2021-09-30_2235 402.0MB 0% 0%
Daily_evening.2021-10-01_2235 27.55MB 0% 0%
Daily_evening.2021-10-02_2235 2.54MB 0% 0%
Weekly_Sat.2021-10-02_2350 198.6GB 2% 3%    <<<<<?
2hourly_even.2021-10-03_1205 3.43MB 0% 0%
2hourly_even.2021-10-03_1405 1.43MB 0% 0%
2hourly_even.2021-10-03_1605 584KB 0% 0%
2hourly_even.2021-10-03_1805 476KB 0% 0%
2hourly_even.2021-10-03_2005 668KB 0% 0%
2hourly_even.2021-10-03_2205 552KB 0% 0%
Daily_evening.2021-10-03_2235 908KB 0% 0%
2hourly_even.2021-10-04_0005 54.95GB 0% 1%
2hourly_even.2021-10-04_0205 193.1GB 2% 3%   >>>?
2hourly_even.2021-10-04_0405 1.08TB 9% 14%    <<<<<<  ??
2hourly_even.2021-10-04_0605 6.23MB 0% 0%
2hourly_even.2021-10-04_0805 11.51MB 0% 0%
2hourly_even.2021-10-04_1005 1.56MB 0% 0%

How can a snapshot size be 1 TB if there was no data deleted, only data was added?

During the timespan of the snapshots above data was being transferred gradually into that volume.

Thank you for your insights,

Bela

[keitha · Accepted solution]

Snapshots grow not when files are deleted but when the filesystem changes. So adding files will cause the snapshots to grow to allow you to revert back to before the files were added if you so desired. Any change will cause snapshots to grow.

[BelaAtCU]

Thank Keith. I think  when it comes to data ingestion to a new volume it maybe the best to take the first snapshot when the data is already in place.  That would conserve a lot of space.

thanks, again,

Bela