zfs discuss - Oct 2008 - recommendations on adding vdev to raidz zpool

I have a 7x150GB drive (+1 spare) raidz pool that I need to expand.
There are 6 open drive bays, so I bought 6 300GB drives and went to
add them as a raidz vdev to the existing zpool, but I didn''t realize
the raidz vdevs needed to have the same number of drives. (why is
that?)

My plan now is to, create a 5 + 1 spare raidz1 vdev with the new
drives, clone all the data over to those, then wipe out the old pool
and create another 5/1 raidz1 to add to the pool. Is this the best way
to do the upgrade or am I overlooking something?

Thanks for the advice!

On Sun, Oct 26, 2008 at 5:31 AM, Peter Baumgartner <sgt.hulka at
gmail.com> wrote:
> I have a 7x150GB drive (+1 spare) raidz pool that I need to expand.
> There are 6 open drive bays, so I bought 6 300GB drives and went to
> add them as a raidz vdev to the existing zpool, but I didn''t
realize
> the raidz vdevs needed to have the same number of drives. (why is
> that?)
They do not have to have the same number of drivers, you can even mix
raidz and plain
disks. That is more a recommendation. Add -f to the command.

On Sun, Oct 26, 2008 at 4:02 AM, Mattias Pantzare <pantzer at ludd.ltu.se>
wrote:
> On Sun, Oct 26, 2008 at 5:31 AM, Peter Baumgartner <sgt.hulka at
gmail.com> wrote:
>> I have a 7x150GB drive (+1 spare) raidz pool that I need to expand.
>> There are 6 open drive bays, so I bought 6 300GB drives and went to
>> add them as a raidz vdev to the existing zpool, but I didn''t
realize
>> the raidz vdevs needed to have the same number of drives. (why is
>> that?)
>
> They do not have to have the same number of drivers, you can even mix
> raidz and plain
> disks. That is more a recommendation. Add -f to the command.
>
What is the risk of creating a pool consisting of two raidz vdevs that
don''t have the same number of disks?

On Sun, Oct 26, 2008 at 3:00 PM, Peter Baumgartner <sgt.hulka at
gmail.com> wrote:
> On Sun, Oct 26, 2008 at 4:02 AM, Mattias Pantzare <pantzer at
ludd.ltu.se> wrote:
>> On Sun, Oct 26, 2008 at 5:31 AM, Peter Baumgartner <sgt.hulka at
gmail.com> wrote:
>>> I have a 7x150GB drive (+1 spare) raidz pool that I need to expand.
>>> There are 6 open drive bays, so I bought 6 300GB drives and went to
>>> add them as a raidz vdev to the existing zpool, but I
didn''t realize
>>> the raidz vdevs needed to have the same number of drives. (why is
>>> that?)
>>
>> They do not have to have the same number of drivers, you can even mix
>> raidz and plain
>> disks. That is more a recommendation. Add -f to the command.
>>
> What is the risk of creating a pool consisting of two raidz vdevs that
> don''t have the same number of disks?
Slightly different reliability and performance on different parts of
the pool. Nothing to worry about in your case.

On Sun, Oct 26, 2008 at 2:00 PM, Peter Baumgartner <sgt.hulka at
gmail.com> wrote:
>>
>> They do not have to have the same number of drivers, you can even mix
>> raidz and plain
>> disks. That is more a recommendation. Add -f to the command.
>>
> What is the risk of creating a pool consisting of two raidz vdevs that
> don''t have the same number of disks?
One risk is that you mistyped the command, when you actually meant
to specify a balanced configuration.

-- 
-Peter Tribble
http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/

On Sun, 26 Oct 2008, Peter Baumgartner wrote:
>>
> What is the risk of creating a pool consisting of two raidz vdevs that
> don''t have the same number of disks?
Virtually no risk.  The only matter of concern would be if the vdevs 
have substantially different I/O performance and latencies since ZFS''s 
load share mechanism will put more data on the vdev which is more 
responsive when the vdevs are under heavy write load.  However, if the 
faster vdev is built with drives of newer design and with higher 
capacity, this behavior may be a good thing.

Bob
=====================================Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/