ZFS pool restructuring and emergency repair

[Xin Li]

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On 06/22/15 17:04, kpneal at pobox.com wrote:
> On Mon, Jun 22, 2015 at 06:13:27PM -0500, Bob Friesenhahn wrote:
>> On Mon, 22 Jun 2015, Quartz wrote:
>> 
>>>> Although in one of Matt Ahrens talks at BSDCan he spoke of
>>>> plans to change this.  Essentially you'ld be able to offline
>>>> a vdev, and a background process (like scrub) would copy all
>>>> the data blocks from that device to elsewhere in the pool.
>>>> Once finished, the devices making up the vdev could be
>>>> physically removed.
>>> 
>>> Oh, that would be nice. Was there a timeline guesstimate for
>>> when that would be implemented, or was it more a "maybe
>>> someday" thing?
>> 
>> This has been planned for perhaps 8 years already.  Still in the
>>  original status.
> 
> Is this via "block pointer rewrite"?

Actually the vdev removal feature is implemented back in last December
(bcc'ed Matt in case he want to chime in) by Delphix.  If I remember
correctly, it's almost finished at the time we had OpenZFS developer
summit last year.

The initial changeset is about 5000 or 5500 lines of changes and is
not integrated into Illumos repository yet.

==

The block pointer rewrite is something that would complicate the ZFS
code quite a lot (and possibly also break many layering design) so
don't expect it happening anytime soon.

Cheers,
- -- 
Xin LI <delphij at delphij.net>    https://www.delphij.net/
FreeBSD - The Power to Serve!           Live free or die
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