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What could/would cause a lack of file-based compression support on a specific pool?



I use drivepool and have had no major issues until this oddity cropped up.
All my non pooled drives seem to support file-based compression fine. all my pools have supported it fine as well (until now) but i recently purchased 2 seagate exos 18tb and made another pool.
for some reason the new pool with the 18tb exos do not support file based compression. checked with fsutil and checked via right click > properties on folders therein.
I'm unsure if this is something expected from enterprise drives or? (all my others are non enterprise). The file system is NTFS so no idea what is going on.
Anyone have anything for me?

non pooled drive

pool with compression working
pool with compression working
pool with compression not working

results in this on the drives and pools working properly (aka all but my T: pool)
and this on the problem child
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okay, so with some digging it turns out ALL of my new 18TB exos were formatted the same way as the rest of my drives.  simple GUI via disk management in windows.   setting the allocation unit size to default.

this always resulted in 4096/4k clusters.  apparently windows sets 8k for drives over a certain size.. or.. something?  because these were all set to that as the default, and i tried a dry run format and opening the dialogue doesnt even present 4k as an option. 

now assuming I wanted to back up 20TB of data then move it back again... how would one (if one could) make 4k cluster size if the GUI doesnt allow it?  Would/could you do it in diskpart?   Why is it not accepted outside of command line?  My 2nd largest drives are 12TB and and 4k all is possible and was set to default there.  so somewhere between 12 & 18 for whatever reason its not a thing?

trying to understand if i have an issue and something went awry or if this is expected/normal behavior?  If its the latter I can leave it, if it is not.. its likely ill have to spend days transferring data around and reformat the things via whatever avenue will afford me the ability to get a 4k cluster size if its possible.

even outside of the shown T pool (2 18tbs) I also have 2 more 18TB disks which are parity drives.  No pooling and nothing on them except a parity file each.  Those too are set to 8k cluster by default with no option for 4k.

what does it all mean?

all drives but the 18tb'ers


all the 18tb disks

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