Combining different ashift values in the same pool

[garachen]

Hello,

I have 4 vdevs of 6 4TB drives each that have been created with an ashift value of 9. The drives are native 512 byte block sized.

I want to add to this pool 4 vdevs of 10 8TB drives. The new drives are native 4K block size. I understand there are performance issues when adding to an existing pool that is mostly full.

Does anyone know if there are additional problems when one pool uses vdevs with different ashift values.

 

[mav@]

I have backup machine with pool including two very different models of disks in RAIDZ vdevs with different number of disks and different ashift sizes. It works fine, but definitely that configuration is not built for speed, only for capacity (I just put there all disks I had). Any imbalance in vdev characteristics, amount of free space, fragmentation, etc. causes write allocation imbalance, that may reduce performance, comparing to uniform pool. On the other side bigger number of disks/vdevs in a pool always improves performance, so if your question is whether to add drives, then the answer is simple: the more -- the better. If you want best performance, it would be good to unload the data somewhere and recreate the pool to clear the fragmentation, but that is not mandatory.

 

[garachen]

Thanks. I'll give it a try then.