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Date:      Sat, 02 Aug 2014 18:33:38 -0400
From:      Daniel Staal <DStaal@usa.net>
To:        freebsd-questions@freebsd.org
Subject:   Re: gvinum raid5 vs. ZFS raidz
Message-ID:  <2D72AC9FF5B82553FEF7D3EB@[192.168.1.50]>
In-Reply-To: <201408020621.s726LsiA024208@sdf.org>
References:  <201408020621.s726LsiA024208@sdf.org>

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--As of August 2, 2014 1:21:54 AM -0500, Scott Bennett is alleged to have 
said:

>>> Does not support migration to any other		Does not support migration
>>> RAID levels or their equivalents.		between raidz levels, even by
>>
>> Correct. Once you have created a vdev, that vdev must remain the same
>> type. You can add mirrors to a mirror vdev, but you cannot add drives or
>> change raid level to raidz1, raidz2, or raidz3 vdevs.
>
>      Too bad.  Increasing the raidz level ought to be not much more
> difficult than growing the raidz device by adding more spindles.  Doing
> the latter ought to be no more difficult that doing it with gvinum's
> stripe or raid5 devices.  Perhaps the ZFS developers will eventually
> implement these capabilities.  (A side thought:  gstripe and graid3
> devices ought also to be expandable in this manner, although the resulting
> number of graid3 components would still need to be 2^n + 1.)

--As for the rest, it is mine.

There actually is a semi-simple way, even if it's not direct...

You can 'send' a ZFS filesystem to a backup drive, and then 'receive' it 
back to a new pool.  It will keep all file and volume level options when 
you do that, but the pools can be set up differently.  It's not something 
you can do in-place, but it's not hard either.

(Basically, it's a simplified 'backup and restore to new setup', but it is 
majorly simplified.)

Daniel T. Staal

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