Jérôme Warnier wrote:
Hi guys,
You can enable compression on a (ZFS) filesystem when already filled
with files. However, it is my understanding that the previously-existing
files are not compressed, only the file added afterwards.
Is there any way to force a "recompression" of the existing files not
already compressed?
Currently no simple way to do it.
You basically have to rewrite every block of every file.
A reasonably safe and simple way to do it is like this, however this
assumes you have sufficient space.
First set the new value for compression.
zfs set compression=on tank/fs
Send a snapshot to a temporary name
zfs snapshot tank/f...@1
zfs send -R tank/f...@1 | zfs recv -vFd tank/fs-recompressed
Mark the original as readonly and send anything newly written
since the 'zfs send' above started.
zfs set readonly=on tank/fs
zfs snapshot tank/f...@2
zfs send -i tank/f...@1 tank/f...@2 | zfs recv -v tank/fs-recompressed
Now delete the original and rename the newone into its place.
zfs delete tank/fs
zfs rename tank/fs-recompressed tank/fs
Note that the new tank/fs will have all the the snapshots of
the original as well since -R was used with the zfs send.
--
Darren J Moffat
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