Hi everyone, I have a small/big problem. Let me explain:

I initially had two 1TB NVMes in a BTRFS RAID 1 as the cache pool, which housed Appdata, System, and ISOs, but nothing else. Since these NVMes were no longer useful, I replaced them with two 2TB NVMes.

The procedure I followed is the standard one recommended by Unraid itself: set the MOVER on each share in the pool from Cache to Array to move the contents of the entire NVMe. Obviously, with all Docker and VM services turned off.

I then replaced the NVMes and then, and I assume this is the error, I recreated the cache pool, not BTRFS but ZFS, with compression and AutoTrim enabled.

So far, everything is fine. I reversed the Mover to copy the entire Appdata, System, ISOs, and domains folders from Array to Cache. And finally, I reactivated the Docker and VM services, and everything restarted correctly.

Everything seems fine so far, but since I have a PLEX Docker, when I moved the appdata folder into the new pool, since I had set ZFS with compression, it compressed all the metadata and the PLEX database, resulting in a slowdown when using Plex. Searches are incredibly slow; for some movies, I can't even see their data page, and there's a general slowdown even when switching from library to library. Before, when I was using BTRFS without compression, it was very fast and without any problems. I've seen various tips online that ZFS compression is indeed harmful for PLEX.

So, after all this explanation, and I apologize for the long-winded nature of it, I'd like to switch back to BTRFS from compressed ZFS.

To do this, is it okay if I do the same thing again, i.e., enable MOVER cache to Array, then format the cache pool in uncompressed BTRFS and transfer everything back? Does Plex data compression remove itself and uncompress it back to how it was before?

I need to fix this as soon as possible because the PLEX service is unusable and my parents are complaining, hahahahaha.

Thanks so much in advance.

Edited November 19, 2025Nov 19 by Digitalfrank

2 hours ago, Digitalfrank said:

To do this, is it okay if I do the same thing again, i.e., enable MOVER cache to Array, then format the cache pool in uncompressed BTRFS and transfer everything back?

Not sure if that is going to help, but the answer is yes.

4 hours ago, Digitalfrank said:

So, after all this explanation, and I apologize for the long-winded nature of it, I'd like to switch back to BTRFS from compressed ZFS.

To do this, is it okay if I do the same thing again, i.e., enable MOVER cache to Array, then format the cache pool in uncompressed BTRFS and transfer everything back? Does Plex data compression remove itself and uncompress it back to how it was before?

Before doing so :

zfs set primarycache=none pool -r
zfs set compression=none pool -r
zfs set direct=always pool -r

zfs rewrite -rv pool

So all your files shall be decompressed, ARC cache (ZFS proper cache within RAM) disabled, and you'll can give it another try.
Else, if performances are still poor, you'll can move your datas already uncompressed peacefully.

Edited November 19, 2025Nov 19 by gyto6

1 hour ago, gyto6 said:

Prima di farlo:

zfs set primarycache=none pool -r
zfs set compression=none pool -r
zfs set direct=always pool -r

zfs rewrite -rv pool

Quindi tutti i tuoi file saranno decompressi, la cache ARC (la cache ZFS vera e propria all'interno della RAM) disabilitata e potrai riprovare.
Altrimenti, se le prestazioni sono ancora scarse, potrai spostare i tuoi dati già decompressi senza problemi.

Thanks everyone for the replies. Just one thing. I'd like to disable compression and decompress the data. However, I'd like to leave ARC enabled since I have 256GB of ECC RAM on this HP server, and therefore, as per Unraid 1/8, I have 32GB of RAM dedicated to ARC, which I think increases ZFS performance.

So, what commands should I use to disable only decompression and decompress the entire pool?

Thanks

5 minutes ago, Digitalfrank said:

Thanks everyone for the replies. Just one thing. I'd like to disable compression and decompress the data. However, I'd like to leave ARC enabled since I have 256GB of ECC RAM on this HP server, and therefore, as per Unraid 1/8, I have 32GB of RAM dedicated to ARC, which I think increases ZFS performance.

So, what commands should I use to disable only decompression and decompress the entire pool?

Thanks

zfs set compression=none pool -r
zfs rewrite -rv pool
zfs rewrite -rv /mnt/pool

Regarding ARC, this implies that you must keep a zfs pool with datas on it to be kept in RAM for read cache when a file is read/written.

Edited November 19, 2025Nov 19 by gyto6
Pool path correction

5 minutes ago, gyto6 said:

zfs rewrite -rv pool

Note that zfs rewrite doesn't work directly on the pool/dataset, it needs the full path, e.g.:

zfs rewrite -r /mnt/tank or zfs rewrite -r /mnt/tank/dataset

ok, but i can excecute command with docker and services while are on or i stop all services and excute command?

2 minutes ago, Digitalfrank said:

ok, but i can excecute command with docker and services while are on or i stop all services and excute command?

Stop the array, so we're sure no depending files are locked in use and can be decompressed.

ok thanks a lot at all.