My ZFS pool consists of two mirrored disks. I have two more disks which I plan to use for rotating offsite backups. The first backup disk was added to the zpool and has nearly completed resilvering.

My question is: if I remove the resilvered backup disk from the machine can I dd it to the second backup disk, and have the resulting disk work as-expected when it's added back into the pool during its rotation? dd would be quite a bit faster than resilvering which is the main reason I'm thinking of doing it (the pool is nearly full and contains a large number of small files).

  • dd would only be significantly faster if the pool was almost full as re-silvering with ZFS arrays only writes the used blocks. Oct 29, 2014 at 11:55
  • @StéphaneChazelas I forgot to mention that is indeed the case in my situation, presently the pool is about 90% full. It also contains a lot of very small files which result in a slower resilvering
    – STW
    Oct 29, 2014 at 12:44

1 Answer 1


No, you can't use dd and have any semblance of safety for your data.

If you're running Oracle Solaris, then you can use the 'zpool split' command. Please see https://docs.oracle.com/cd/E36784_01/html/E36835/gjooc.html for details

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