What determines the size of a snapshot?

[beneix]

I have a series of snapshots going back to 24.7.1. Their sizes vary greatly, and I would like to understand why and if there is anything I can do to influence the size.

[Monviech (Cedrik)]

The delta is your current active zfs pool vs the snapshot zfs pool for each of these snapshots.

Try marking a different one as active and you will see all values change to the delta of the new active one.

So the more files change the larger they get over time.

[beneix]

So the more files change the larger they get over time.

Thanks, but looking at my list the size goes 903M -> 3.67G -> 1.17G -> 804M in date order from 30/8 to 27/10. That doesn't constitute a constant increase. Is this because updates replace some larger files with smaller ones? I have not made any configuration changes of my own between these snapshots.

[Monviech (Cedrik)]

The delta is always to your current active zpool.

These snapshots are not incremental and not in a chain relationship to each other, they are differential.

Some of them replace a lot of files and the kernel so the delta will be larger than for others.

Also I think a lot of logging will inflate them too. Keeping them around too long will make you run out of space eventually.

[Patrick M. Hausen]

And they are on the ZFS block and not on the file level.