How to upgrade a ZFS RAID-Z array to larger disks on OpenSolaris

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I'm planning on installing OpenSolaris on my home server (right now it has Linux) and I would like to know how to prepare for upgrading the server to have larger hard drives in the future. Now the server has 4x 400GB SATA drives and I would install OpenSolaris with ZFS RAID-Z on them. Some time later this or next year I'm going to upgrade the drives to maybe 4x 1TB SATA drives.

How can I do the upgrading and increasing of the partition size with ZFS? Is it a simple and painless operation (e.g. replace one drive at a time and ZFS will automatically resize itself to use the full space), or are some special steps required? Can it be done without shutting down the system?

Best Answer

  1. Offline drive #1.
  2. Replace the old drive with the newer, high-capacity drive.
  3. zpool replace the drive.
  4. Wait for the replacement to be rebuilt.
  5. Goto step 1 and repeat for each successive drive in the array.

You may need to export and then import the zpool once this procedure is complete; the pool will then show the increased size. No downtime is required, but if a drive does go south while you're upgrading your array, you will lose everything, as with four total disks you presumably have a 3+1 setup. (The odds aren't that high, but Murphy never sleeps.)

The official source: "Replacing Devices in a Storage Pool" in the ZFS Administration Guide. The ZFS Best Practices Guide is also useful.

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