ZFS RAID 10 capacity expansion and uneven data distribution

[Daniel Kalchev]

Not a total bs, but.. it could be made simpler/safer.

skip 2,3,4 and 5
7a. zfs snapshot -r zpool.old at send
7b. zfs send -R zpool.old at send | zfs receive -F zpool
do not skip 8 :)
11. zpool attach zpool da1 da2 && zpool attach zpool da3 da4

Everywhere in the instruction where it says daX replace with gpt/zpool-daX as in the original config.

After this operation, you should have the exact same zpool, with evenly redistributed data. You could use the chance to change ashift etc. Sadly, this works only for mirrors.

Important to understand that since the first step you have an non-redundant pool. It’s very reasonable to do a scrub before starting this process and of course have usable backup.

Daniel

> On 14.05.2015 г., at 16:42, Gabor Radnai <gabor.radnai at gmail.com> wrote:
> 
> Hi Kai,
> 
> As others pointed out the cleanest way is to destroy / recreate your pool
> from backup.
> 
> Though if you have no backup a hackish, in-place recreation process can be
> the following.
> But please be *WARNED* it is your data, the recommended solution is to use
> backup,
> if you follow below process it is your call - it may work but I cannot
> guarantee. You can
> have power outage, disk outage, sky falling down, whatever and you may lose
> your data.
> And this may not even work - more skilled readers could bit me on head how
> stupid this is.
> 
> So, again be warned.
> 
> If you are still interested:
> 
>> On one server I am currently using a four disk RAID 10 zpool:
>> 
>> 	zpool              ONLINE       0     0     0
>> 	  mirror-0         ONLINE       0     0     0
>> 	    gpt/zpool-da2  ONLINE       0     0     0
>> 	    gpt/zpool-da3  ONLINE       0     0     0
>> 	  mirror-1         ONLINE       0     0     0
>> 	    gpt/zpool-da4  ONLINE       0     0     0
>> 	    gpt/zpool-da5  ONLINE       0     0     0
> 
> 
> 1. zpool split zpool zpool.old
> this will leave your current zpool composed from slice of da2 and da4, and
> create a new pool from da3 and da5.
> 2. zpool destroy zpool
> 3. truncate -s <proper size> /tmp/dummy.1 && truncate -s <proper size>
> /tmp/dummy.2
> 4. zpool create <flags> zpool mirror da2 /tmp/dummy.1 mirror da4
> /tmp/dummy.2
> 5. zpool zpool offline /tmp/dummy.1 & zpool offline /tmp/dummy.2
> 6. zpool import zpool.old
> 7. (zfs create ... on zpool as needed) copy your stuff from zpool.old to
> zpool
> 8. cross your fingers, *no* return from here !!
> 9. zpool destroy zpool.old
> 10. zpool labelclear da3 && zpool labelclear da5 # just to be on clear side
> 11. zpool replace zpool /tmp/dummy.1 da3 && zpool replace zpool
> /tmp/dummy.2 da5
> 12. wait for resilver ...
> 
> If this is total sh*t please ignore, i tried it in VM seemed to work.
> 
> Thanks.
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