[OpenIndiana-discuss] System Panics after deleting zvol

[matt at focusedmobile.com]

> You can use "dd" for zvols and "rsync" for filesystem datasets, if
> you don't have any snapshots to "zfs send" from the pool while it
> is mounted read-only (a year ago I had problems sending from such
> a readonly pool, because intermittent "zfs hold" failed; I think
> the problem was addressed in more recent builds of illumos and OI).
>
> If you want to recreate the snapshot/clone structure on the target
> pool, you can somewhat emulate this with rsync, by copying from
> the /$pool/$dataset/.zfs/snapshots/$snapname/ directories with
> "rsync -cavPHK --delete-after ./ remote:/targetpath/" and making
> the snapshots or clones manually on the target when appropriate
> between such rsync runs. For slow net and compressible data you
> might also benefit from "rsync -z" for gzip compression.
>
> I am not sure you can process differences of zvols as cleanly if
> you need the history; maybe rsync of the zvols' character device
> files can help in this case...
>
> HTH,
> //Jim Klimov

I did find a snapshot I had created a few months back, last night I 
created a 3TB pool with some spare disks and am using zfs send to copy 
the zvol over to the new pool.  This time without dedupe.. let you know 
how it goes, once I get the data off then I'll recreate the pool with 
out dedupe.  What is a good formula to use to know how much memory a 
system should have to properly dedupe and more importantly walk back any 
zvol deletions?