ZFS unable to import pool

[Karl Denninger]

On 4/23/2014 10:03 AM, Tom Evans wrote:
> On Wed, Apr 23, 2014 at 3:21 PM, Karl Denninger <karl at denninger.net> wrote:
>> /*Filesystem based "redundancy" is not a backup strategy!*/
>>
> It's my (home) backup strategy :(
>
> Very few cost efficient ways to backup 15TB+ of data other than
> redundant spinning rust.
>
I have a large home system as well.

But I do back it up to other spinning pieces of rust, and rotate the 
backups out to a bank safe-deposit box.  If I make a terrible mistake 
(or my hardware and/or software does) I have a means of recovery.  There 
are no guarantees of course in that I COULD wind up with a bad disk in 
the safe deposit box, but if my house burns down I have a shot at 
recovery with high odds of success -- an act that would otherwise be 
impossible.  Partitioning my data off into "essentially archival, 
read-almost-only" and "active" means that the former needs to be updated 
rarely and the former is of small enough size that I don't go crazy 
doing it either in money or time.

And I *HAVE* had things like this happen -- twice in the last 20 years 
I've had a disk adapter go insane and scribble on MULTIPLE spindles at 
once.  There is no RAID strategy that will protect you against this 
event; you either have a backup or you're done.

ZFS actually makes this easier with send/receive and the ability to 
import a pool, send to it and then export it.  The backup pool can have 
compression turned on where for performance reasons it may not make 
sense for the online pool to do so.  And you can rotate that out fairly 
easily too; you can take a 2-way mirror, add a third disk and let it 
resilver, then split the third one off and remove it, giving you a 
dismounted copy you can then stick in a box and yet if you need it -- 
it's there.

-- 
-- Karl
karl at denninger.net


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