zfs discuss - Jun 2007 - Can you create a degraded raidz vdev?

I have 6 400GB discs and want to make two RAIDZ 2/1 vdevs out of them (ie
2stripe 1parity).

The problem is that 4 are in use... so I want to do something like:

  zpool create datadump raidz c1t0d0 c1t1d0 missing

Then move and bunch of data into datadump, to free up another two discs, then

  zpool add datadump raidz c1t2d0 c1t3d0 missing

Now move the rest of the data over, freeing the last two drives which I would
then add as spares to let zfs complete the parity of those vdevs.

Is this currently possible?

--
Cheers
Paul
 
 
This message posted from opensolaris.org

On 6/14/07, Paul Hedderly <paul+os at mjr.org>
wrote:
>
> Is this currently possible?
You may be able to do this my specifying a sparse file for the last
device, and then immediately issuing a "zpool offline" of it after the
pool is created.  It seems to work, and I was able to create a pool
that way with no complaints.

You can create a 400GB sparse file with something like:

dd if=/dev/zero bs=1024k count=1 seek=400000 of=/path/to/vdev_file

Unfortunately, tmpfs doesn''t seem to support sparse files, and while
it did appear to work on a ZFS filesystem, I''m not sure if it is a
good idea.  (I don''t have any UFS filesystems.)  Perhaps someone else
can comment on this?

Still, you will have no redundancy during this operation, so I hope
you have backups.

Chris Csanady

Chris Csanady wrote:
> On 6/14/07, Paul Hedderly <paul+os at mjr.org> wrote:
>>
>> Is this currently possible?
> 
> You may be able to do this my specifying a sparse file for the last
> device, and then immediately issuing a "zpool offline" of it
after the
> pool is created.  It seems to work, and I was able to create a pool
> that way with no complaints.
> 
> You can create a 400GB sparse file with something like:
> 
> dd if=/dev/zero bs=1024k count=1 seek=400000 of=/path/to/vdev_file
Alternatively:
mkfile -n 400g

--matt

Hi Paul,

I think I have a smiliar problem, I have 4 disks, two empty, two full
and want to create a RAIDZ1 from these disk.

But I''m new to zfs, maybe you can explain me how do you done it, if it
runs :)

Thanks in advance :)


Greetings Cyron
> I have 6 400GB discs and want to make two RAIDZ 2/1 vdevs out of them
> (ie 2stripe 1parity).
> 
> The problem is that 4 are in use... so I want to do something like:
> 
>   zpool create datadump raidz c1t0d0 c1t1d0 missing
> 
> Then move and bunch of data into datadump, to free up another two
> discs, then
> 
>   zpool add datadump raidz c1t2d0 c1t3d0 missing
> 
> Now move the rest of the data over, freeing the last two drives which
> I would then add as spares to let zfs complete the parity of those
> vdevs.
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