Rich Freeman on 22 Feb 2013 19:12:49 -0800

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Re: [PLUG] Solaris backup/restore

On Fri, Feb 22, 2013 at 8:41 PM, Eric at <> wrote:
> I am unable to elaborate other than to say that I think it has to do with
> the nature of zfs which is not a filesystem per se, but more like a
> combination of a file system and a logical volume manager.

If you actually dd the raw device it shouldn't matter, unless there is
data being stored somewhere other than on the drive (I guess it is
possible - partition table in flash or something?).  When you dd one
drive onto another the drives are from an OS-perspective identical
(again, unless it is looking at something other than what is stored on
the drive itself).  Now, images are inconvenient, slow, wasteful, etc.
 When restoring them you usually can't do anything but put them on a
like (or larger) drive - they're hard to manipulate unlike a tarball
or something more sensible.  The one thing they do accomplish is
giving you an identical drive to what you started with - again
assuming you dd the raw device.  If you dd just a partition or you dd
some kind of higher-level logical device exposed by zfs or something
then all bets are off unless you re-create everything underneath

> Aside: I found out the system in question uses UFS, not ZFS.  What does
> that mean?  I have no idea.  But soon I will!

Just another filesystem - common on Unix variants.  I believe the
various BSDs use it, or what on wikipedia appears to be a derivative
of it.  Likely comparable to something like ext2.  I'm not sure if it
even supports journaling though.  If you're running Solaris I can't
imagine why you wouldn't use ZFS.  I'm holding out for btrfs which
will be more feature-complete but that's only because I have ext4 to
hold me over.

BTW - not sure if anybody saw the news but they merged raid5/6 into
btrfs, and it apparently supports reshaping.  Those were the two
features missing from ZFS which were really holding me back from
considering it.  Of course, it will still be time before I'd trust
btrfs with my data, but it is looking better and better.  (ZFS does
let you add and remove RAID-Z arrays from a filesystem, but to enlarge
an array you either have to add a whole new array or add some drive to
hold your data, remove the old array, create a new array, and remove
the temporary drive.  When I say reshaping I mean in the sense of
adding one more drive to a RAID5/6 and therefore getting the full
capacity of the new drive as additional space.)

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