On Wed, May 05, 2010 at 04:34:13PM -0400, Edward Ned Harvey wrote: > The suggestion I would have instead, would be to make the external drive its > own separate zpool, and then you can incrementally "zfs send | zfs receive" > onto the external.
I'd suggest doing both, to different destinations :) Each kind of "backup" serves different, complementary purposes. > #1 I think all the entire used portion of the filesystem needs to resilver > every time. I don't think there's any such thing as an incremental > resilver. Incorrect. It will play forward all the (still-live) blocks from txg's between the time it was last online and now. That said, I'd also recommend a scrub on a regular basis, once the resilver has completed, and that will trawl through all the data and take all that time you were worried about anyway. For a 200G disk, full, over usb, I'd expect around 4-5 hours. That's fine for a "leave running overnight" workflow. This is the benefit of this kind of "backup" - as well as being almost brainless to initiate, it's able to automatically repair marginal sectors on the laptop disk if they become unreadable, saving you from the hassle of trying to restore damaged files. The send|recv kind of backup is much better for restoring data from old snapshots (if the target is larger than the source and keeps them longer), and recovering from accidentally destroying both mirrored copies of data due to operator error. > #2 How would you plan to disconnect the drive? If you zpool detach it, I > think it's no longer a mirror, and not mountable. That's correct - which is why you would use "zpool offline". -- Dan.
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