Size on Disk differs from Freenas 11.1 to Scale 22.02.4

[zenon1823]

I used rsync to move the contents of a datastore from my old Freenas 11.1u6 server to my new Scale 22.02.4 server.
When I checked the folder properties for a random (large) folder the files counts and size match perfection, but Size on Disk is drastically different.
see attached image:
Freenas 11.1
File count: 63,755
Size: 195GB
Size on Disk: 233GB

Scale 22.02.4
File count: 63,755
Size: 195GB
Size on Disk: 192GB

Both datastores are using L4Z compression, both are showing 1.03 ratio.
The freenas pool is Raidz1 the Scale pool is mirrors

I donl't think it really matters, but im curious what am i missing here?
Does Size on Disk for a RAIDZ pool also include the parity space maybe?
195GB to 192GB is about a 2% reduction in space. Is that the effect of compression?

 

[artlessknave]

you probably had files that weren't compressed. sending them all to a new pool would have compressed all the newly written data.
data at rest is never re-compressed, so if you change compression settings, everything stays the same until it's written to, which will copy-on-write the whole file to a new, compressed location.
replication would probalby have been a better experience than rsync....