I tried to find a more applicable community to post this to but didn’t find anything.
I recently set up a NAS/server on a Raspberry Pi 5 running Raspberry Pi OS (see my last post) and since then I’ve got everything installed into a 3D printed enclosure and I’ve got RAID set up (ZFS RAIDz1). Prior to setting up RAID, I could transfer files to/from the NAS at around 200MB/s, but now that RAID is seemingly working things are transferring at around 28-30 MB/s. I did a couple searches and found someone suggesting to disable sync ($ sudo zfs set sync=disabled zfspool). I tried that and it doesn’t seem to have had any effect. Any suggestions are welcome but keep in mind that I barely know what I’m doing.
Edit: When I look at the SATA hat, the LEDs indicate that the drives are being written to for less than half a second and then there’s a break of about 4 seconds where there’s no writing going on.
I don’t know what ARC is and my searches so far haven’t helped. The CPU usage is pretty low, on htop is rarely passes 10%.
Edit: I asked chatGPT what it means, this seems like exactly the setting I was hoping to find. I’ll check it out and post an update.
Edit2: I changed the ARC size to 8GB and it definitely seems to have gotten slower.
this is the limits of a slow interface and 5 drives. See my other reply to enable faster pci speeds. because of how zfs works 5 drives is slower than 3, takes more cache and write speeds especially will be slower, quite a lot slower. with 5 drives and 16gb you can easily have a zfs cache of 12 gigs to help it along, i guess this is why you are getting large gaps between writes. as someone else said a pi doesn’t do well in this case but I reckon you can improve it. however as also said it is never going to be a speedy solution. secure and safe for data but not fast
ARC is the in-memory cache used by ZFS. If it’s completely off the effect can be dramatic. Under no circumstances should a larger cache cause anything to get slower, ever. Even the raspi didn’t have memory that is that slow that this is a reasonable outcome. By default on most distros, ARC size is capped to 50% of physical system memory. Keep in mind it is a cache: if something else needs needs the RAM, it will be released.
As a concrete example: I was recently working on a server where a maintenance task that should take like 12hrs or so at the worst somehow took 2 weeks (!) and still wasn’t finished. That was ARC being disabled.