ZFS and mv utility

[Pawel Jakub Dawidek]

On Thu, Apr 26, 2007 at 12:56:50AM +0400, Alexey Tarasov wrote:
> Hello Pawel.
> 
> I have a question about ZFS and mv utility. I have the following pool configuration:
> 
> NAME                          USED  AVAIL  REFER  MOUNTPOINT
> storage                      62,1G   121G    26K  /storage
> storage/music                7,95G   121G  7,95G  /storage/music
> storage/oldhome              47,5G   121G  47,5G  /storage/oldhome
> 
> I made the following operation: mv /storage/oldhome/lexa/music/* /storage/music and that operation took a very long time. It seems that MV copies files first from 
> storage/oldhome/lexa/musc to storage/music and then deletes them from old location. But I move files within one storage pool and it should work as fast, as it works on UFS 
> partition. Does it need to be modified for compatibility with ZFS?

From mv(1) manual page:

     As the rename(2) call does not work across file systems, mv uses cp(1)
     and rm(1) to accomplish the move.  The effect is equivalent to:

           rm -f destination_path && \
           cp -pRP source_file destination && \
           rm -rf source_file

ZFS pool is not a file system. Look at mount(8) output. It would be
possible in theory to move data faster within one pool and this was
discussed on zfs-discuss at opensolaris.org, you may want to search the
archives.

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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