Comment by paulmd
6 years ago
> Writes in a raidz are always limited to a single disk’s performance
what? no. why would that be the case? You lose a single disk's performance due to the checksumming.
just from my personal NAS I can tell you that I can do transfers from my scratch drive (NVMe SSD) to the storage array at more than twice the speed of any individual drive in the array... and that's in rsync which is notably slower than a "native" mv or cp.
The one thing I will say is that it does struggle to keep up with NVMe SSDs, otherwise I've always seen it run at drive speed on anything spinning, no matter how many drives.
> what? no. why would that be the case? You lose a single disk's performance due to the checksumming.
I think they are probably referring to the write performance of a RAIDZ VDEV being constrained by the performance of the slowest disc within the VDEV.
true, if you have 7 fast disks and one slow disk in a raidz, you get 7 x slow disk performance.