vDev add - different numbers of drives

[gecko1a]

Hallo,

My config:

N4F 9.1.0.1 - Sandstorm (revision 847) - Full install
- vDev1 4x 2TB RaidZ1
- vDev2 4x 2TB RaidZ1

Pool vDev1 + vDev2 (vDev add)
There are 9TB data in Pool

Now I want add vDev3 3x 2TB RaidZ1 to Pool, but I read "It recommends adding the same number of drives as the existing virtual device." below the feature.

What could by wrong, if I add a different numbers of drives?
Or have I to add a vDev with 4x 2TB or with 2x 4x 2TB drives?

What is the risk, if I add only 3 HDs?

Thanks and regards

gecko

[raulfg3]

What could by wrong, if I add a different numbers of drives?

Nothing can be wrong, it's only recommended, to facilitate future migration to big disk and to mantain Troughput.

one pool that have diferent vdev , speed is the low speed of the lowest vdev, because of this, recomendations is to use same number of disk.

Please read this excelent article: http://constantin.glez.de/blog/2010/06/ ... erformance

[gecko1a]

Thanks for the link. It's usefull to understand

In my case max. performance is not the goal. So I will add a vDev with 3 Disk to my Pool.