I know that setting
dedup=on causes high memory usage and that it's almost never worth it (see e.g. https://serverfault.com/a/569099/208661). However I did turn it on in order to see how it works and put 20 GB on a 1.4 TB pool with a cache. The memory consumption (difference of memory usage after boot with and without zfs) is approx. 8 GB higher than with
btrfs. After setting
dedup=on it was noticable higher than with
btrfs, but not 8 GB. Now, I turned
off and rebooted, but the memory consumption is still high (I'd say the same).
Will it remain high, i.e. do I have to destroy and recreate the pool in order to avoid this memory consumption, will it take time until it does down, can I do something (some sort of re-duplication) in order to speed up the process?