I’m syncoiding from my normal RAIDz2 to a backup mirror made of 2 disks. I looked at zpool iostat and I noticed that one of the disks consistently shows less than half the write IOPS of the other:
capacity operations bandwidth
pool alloc free read write read write
------------------------------------ ----- ----- ----- ----- ----- -----
storage-volume-backup 5.03T 11.3T 0 867 0 330M
mirror-0 5.03T 11.3T 0 867 0 330M
wwn-0x5000c500e8736faf - - 0 212 0 164M
wwn-0x5000c500e8737337 - - 0 654 0 165M
This is also evident in iostat:
f/s f_await aqu-sz %util Device
0.00 0.00 3.48 46.2% sda
0.00 0.00 8.10 99.7% sdb
The difference is also evident in the temperatures of the disks. The busier disk is 4 degrees warmer than the other. The disks are identical on paper and bought at the same time.
Is this behaviour expected?
B350 isn’t a very fast chipset to begin with
For sure.
I’m willing to bet the CPU in such a motherboard isn’t exactly current-gen either.
Reasonable bet, but it’s a Ryzen 9 5950X with 64GB of RAM. I’m pretty proud of how far I’ve managed to stretch this board. 😆 At this point I’m waiting for blown caps, but the case temp is pretty low so it may end up trucking along for surprisingly long time.
Are you sure you’re even running at PCIe 3.0 speeds too?
So given the CPU, it should be PCIe 3.0, but that doesn’t remove any of the queues/scheduling suspicions for the chipset.
I’m now replicating data out of this pool and the read load looks perfectly balanced. Bandwidth’s fine too. I think I have no choice but to benchmark the disks individually outside of ZFS once I’m done with this operation in order to figure out whether any show problems. If not, they’ll go in the spares bin.
Oh wow congrats, I’m currently in the struggle of stretching an ab350m to accept a 4600G and failing.
You’re right, you should hit PCIe 3 speeds and it’s weird, but the fact that the drives swap speeds depending on how they’re plugged in points to either drivers or the chipset.
On paper it should support it. I’m assuming it’s the ASRock AB350M. With a certain BIOS version of course. What’s wrong with it?
It’s a gigabyte ab350m gaming-3 rev 1.0. it boots grub fine but then crashes right after displaying “loading Linux 6.x”, CPU led flashes then dram led stays on, I have to turn it off with the PSU switch.
Either it’s a rev 1.0 bug which is a thing on those motherboards, or the CPU (or igpu) is defective.
https://superuser.com/questions/1854228/proxmox-doesnt-boot-after-cpu-change
I’m currently waiting on support from both the seller and gigabyte but I don’t expect anything out of it, though I’m still yet to test it in a different motherboard.
