Re: [zfs-discuss] Mirroring raidz ?

2011-01-12 Thread Bob Friesenhahn

On Tue, 11 Jan 2011, Jorgen Lundman wrote:


It would be nice to create a setup similar to

zpool create sub1 raidz c0t0d0 c0t1d0 c0t2d0 c0t3d0 c0t4d0 c0t5d0
zpool add sub1 raidz c0t6d0 c0t7d0 c0t8d0 c0t9d0 c0t10d0 c0t11d0

zpool create sub2 raidz c1t0d0 c1t1d0 c1t2d0 c1t3d0 c1t4d0 c1t5d0
zpool add sub2 raidz c1t6d0 c1t7d0 c1t8d0 c1t9d0 c1t10d0 c1t11d0

zpool create pool mirror sub1 sub2

As I could lose a HDD in either external drive cage, or indeed a whole external 
drive cage (controller/cable/power) without downtime.

But I have a feeling I can not do this? What would be recommended?


Nothing is impossible (if you are willing to do part of this outside 
of zfs) but it is really not so wise to create huge mirror devices 
like this.  It is much better to construct mirror pools using many 
smaller devices directly.  The reason is that if something goes wrong, 
the failure is more isolated and resilver times are dramatically 
improved.  Overall performance will be improved.


The recommendation would be to add many mirror vdevs such as 
c0t0d0/c1t0d0.  The wasted space would be a bit less than 
what you proposed since it would avoid the raidz overhead.


Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,http://www.GraphicsMagick.org/
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[zfs-discuss] Mirroring raidz ?

2011-01-12 Thread Jorgen Lundman
I have a server, with two external drive cages attached, on separate 
controllers:

c0::dsk/c0t0d0 disk connectedconfigured   unknown
c0::dsk/c0t1d0 disk connectedconfigured   unknown
c0::dsk/c0t2d0 disk connectedconfigured   unknown
c0::dsk/c0t3d0 disk connectedconfigured   unknown
c0::dsk/c0t4d0 disk connectedconfigured   unknown
c0::dsk/c0t5d0 disk connectedconfigured   unknown
c0::dsk/c0t6d0 disk connectedconfigured   unknown
c0::dsk/c0t7d0 disk connectedconfigured   unknown
c0::dsk/c0t8d0 disk connectedconfigured   unknown
c0::dsk/c0t9d0 disk connectedconfigured   unknown
c0::dsk/c0t10d0disk connectedconfigured   unknown
c0::dsk/c0t11d0disk connectedconfigured   unknown

c1::dsk/c1t1d0 disk connectedconfigured   unknown
c1::dsk/c1t2d0 disk connectedconfigured   unknown
c1::dsk/c1t3d0 disk connectedconfigured   unknown
c1::dsk/c1t4d0 disk connectedconfigured   unknown
c1::dsk/c1t5d0 disk connectedconfigured   unknown
c1::dsk/c1t6d0 disk connectedconfigured   unknown
c1::dsk/c1t7d0 disk connectedconfigured   unknown
c1::dsk/c1t8d0 disk connectedconfigured   unknown
c1::dsk/c1t9d0 disk connectedconfigured   unknown
c1::dsk/c1t10d0disk connectedconfigured   unknown
c1::dsk/c1t11d0disk connectedconfigured   unknown

It would be nice to create a setup similar to

zpool create sub1 raidz c0t0d0 c0t1d0 c0t2d0 c0t3d0 c0t4d0 c0t5d0
zpool add sub1 raidz c0t6d0 c0t7d0 c0t8d0 c0t9d0 c0t10d0 c0t11d0

zpool create sub2 raidz c1t0d0 c1t1d0 c1t2d0 c1t3d0 c1t4d0 c1t5d0
zpool add sub2 raidz c1t6d0 c1t7d0 c1t8d0 c1t9d0 c1t10d0 c1t11d0

zpool create pool mirror sub1 sub2

As I could lose a HDD in either external drive cage, or indeed a whole external 
drive cage (controller/cable/power) without downtime.

But I have a feeling I can not do this? What would be recommended?
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Re: [zfs-discuss] Mirroring raidz ?

2011-01-11 Thread Benji
24 disks, 2 controllers. You could create a mirrored pool of 12 vdevs, e.g.

zpool create tank mirror c0t0d0 c1t1d0
zpool add tank mirror c0t1d0 c1t2d0
...

Alternating between the 2 controllers for each mirror so that when one 
controller fails, the pool would become degraded but still available.

You would lose half the storage space to mirroring, but would gain better 
redundency, in my opinion. It all depends on the application of your pool. 

Otherwise, create 2 raidz-2 vdevs and add the second one the the pool.

Hope that helps ;)
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