zfs discuss - Jan 2008 - Break a ZFS mirror and concatenate the disks

We have a ZFS mirror setup of two 73GB''s disk, but we are running out
of space.  I want to break the mirror and join the disk to have a pool of 146GB,
and of course not lose the data doing this.  What are the commands?
To break the mirror I would do
 
zpool detach moodle c1t3d0
 
       NAME        STATE     READ WRITE CKSUM
        moodle      ONLINE       0     0     0
          mirror    ONLINE       0     0     0
            c1t2d0  ONLINE       0     0     0
            c1t3d0  ONLINE       0     0     0

Then could I do 
zpool add moodle c1t3d0

without losing the data?
 
 
This message posted from opensolaris.org

Hey Kory,

I think you must mean can you detach one of the 73GB disks from moodle 
and then add it to another pool of 146GB and you want to save the
data from the 73GB disk?

You can''t do this and save the data. By using zpool detach, you are
removing any knowledge of ZFS from that disk.

If you want to save the data from moodle, I would add new disks to
this pool, either by replacing the 73GB disks with large disks
or by adding another mirror, like this:

# zpool replace moodle c1t2d0 c2t2d0
# zpool replace moodle c1t3d0 c2t3d0

or:

# zpool add moodle mirror c2t2d0 c2t3d0

Maybe I misunderstand what you are trying to do...

Cindy

Kory Wheatley wrote:
> We have a ZFS mirror setup of two 73GB''s disk, but we are running
out of space.  I want to break the mirror and join the disk to have a pool of
146GB, and of course not lose the data doing this.  What are the commands?
> To break the mirror I would do
>  
> zpool detach moodle c1t3d0
>  
>        NAME        STATE     READ WRITE CKSUM
>         moodle      ONLINE       0     0     0
>           mirror    ONLINE       0     0     0
>             c1t2d0  ONLINE       0     0     0
>             c1t3d0  ONLINE       0     0     0
> 
> Then could I do 
> zpool add moodle c1t3d0
> 
> without losing the data?
>  
>  
> This message posted from opensolaris.org
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss

(I think Cindy is thinking of something else :-)

Kory Wheatley wrote:
> We have a ZFS mirror setup of two 73GB''s disk, but we are running
out of space.  I want to break the mirror and join the disk to have a pool of
146GB, and of course not lose the data doing this.  What are the commands?
> To break the mirror I would do
>  
> zpool detach moodle c1t3d0
>  
>        NAME        STATE     READ WRITE CKSUM
>         moodle      ONLINE       0     0     0
>           mirror    ONLINE       0     0     0
>             c1t2d0  ONLINE       0     0     0
>             c1t3d0  ONLINE       0     0     0
> 
> Then could I do 
> zpool add moodle c1t3d0
> 
> without losing the data?
Yes.  This is exactly how to do that.  Later, of course,
you can attach more disks to protect the data with mirrors.
  -- richard

Currently c2t2d0 c2t3d0 are setup in a mirror.  I want to break the mirror and
save the data on c2t2d0 (which both drives are 73g.  Then I want to concatenate
c2t2do to c2t3d0 so I have a pool of 146GB no longer in a mirror just
concatenated.  But since their mirror right now I need the data save on one disk
so I don''t lose everything.  I don''t need to add new disks
that not an option I want to break the mirror so I can expand the disks together
in a pool but save the data.
 
 
This message posted from opensolaris.org

Hi Kory,

Yes, I get it now. You want to detach one of the disks and then readd 
the same disk, but lose the redundancy of the mirror.

Just as long as you realize you''re losing the redundancy.

I''m wondering if zpool add will complain. I don''t have a
system to
try this at the moment.

Cindy

Kory Wheatley wrote:
> Currently c2t2d0 c2t3d0 are setup in a mirror.  I want to break the mirror
and save the data on c2t2d0 (which both drives are 73g.  Then I want to
concatenate c2t2do to c2t3d0 so I have a pool of 146GB no longer in a mirror
just concatenated.  But since their mirror right now I need the data save on one
disk so I don''t lose everything.  I don''t need to add new
disks that not an option I want to break the mirror so I can expand the disks
together in a pool but save the data.
>  
>  
> This message posted from opensolaris.org
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss

Kory,
> Yes, I get it now. You want to detach one of the disks and then readd
> the same disk, but lose the redundancy of the mirror.
>
> Just as long as you realize you''re losing the redundancy.
>
> I''m wondering if zpool add will complain. I don''t have a
system to
> try this at the moment.
The correct, just verified steps are as follows:

zpool detach moodle c2t3d0
zpool add moodle c2t3d0

I performed these steps  while the zpool was online, under heavy I/O,  
with an I/O tool that does data validation. When done, I then  
performed a final "zpool scrub moodle", with no issues, and then  
revalidated all the data.

As stated earlier, sacrificing redundancy (RAID 1 mirroring) for  
double the storage (RAID 0 concatenation) is being penny wise, and  
pound foolish.

Jim
>
> Cindy
>
> Kory Wheatley wrote:
>> Currently c2t2d0 c2t3d0 are setup in a mirror.  I want to break the  
>> mirror and save the data on c2t2d0 (which both drives are 73g.   
>> Then I want to concatenate c2t2do to c2t3d0 so I have a pool of  
>> 146GB no longer in a mirror just concatenated.  But since their  
>> mirror right now I need the data save on one disk so I don''t
lose
>> everything.  I don''t need to add new disks that not an option
I
>> want to break the mirror so I can expand the disks together in a  
>> pool but save the data.
>>
>>
>> This message posted from opensolaris.org
>> _______________________________________________
>> zfs-discuss mailing list
>> zfs-discuss at opensolaris.org
>> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss