[smartos-discuss] an interesting survey -- the zpool with most disks you have ever built

[Richard Elling]

> On Mar 3, 2016, at 8:35 PM, Fred Liu <Fred_Liu at issi.com> wrote:
> 
> Hi,
> 
> Today when I was reading Jeff's new nuclear weapon -- DSSD D5's CUBIC RAID introduction,
> the interesting survey -- the zpool with most disks you have ever built popped in my brain.

We test to 2,000 drives. Beyond 2,000 there are some scalability issues that impact failover times.
We’ve identified these and know what to fix, but need a real customer at this scale to bump it to
the top of the priority queue.

> 
> For zfs doesn't support nested vdev, the maximum fault tolerance should be three(from raidz3).

Pedantically, it is N, because you can have N-way mirroring.

> It is stranded if you want to build a very huge pool.

Scaling redundancy by increasing parity improves data loss protection by about 3 orders of 
magnitude. Adding capacity by striping reduces data loss protection by 1/N. This is why there is
not much need to go beyond raidz3. However, if you do want to go there, adding raidz4+ is 
relatively easy.
 — richard


--

Richard.Elling at RichardElling.com
+1-760-896-4422