I manually started a scrub to check the system performance. Before starting the scrub htop showed this:
Afterwards it’s like this:
So there’s around 25% CPU usage by the kernel and memory usage is about 15%. Doesn’t look to me like this is the bottleneck.
However, for some reason the scrub seems to go faster now:
scan: scrub in progress since Tue Sep 14 12:26:56 2021
484G scanned at 1.41G/s, 55.1G issued at 165M/s, 3.18T total
0B repaired, 1.69% done, 05:31:17 to go
Maybe it had something to do with the fact that a replication started while the original scrub was going on? This suggests that accessing or writing data to the pool will kill the scrub performance.
Anyways, I’m not gonna pursue this any further, it’s just not worth the time.