Hey fellow Selfhosters! I need some help, I think, and searching isn’t yielding what I’m hoping for.
I recently built a new NAS for my network with 4x 18TB drives in a ZFS raidz1 pool. I previously have been using an external USB 12TB harddrive attached to a different machine.
I’ve been attempting to use rsync to get the 12TB drive copied over to the new pool and things go great for the first 30-45 minutes. At that point, the current copy speed diminishes and 4 current files in progress sit at 100% done. Eventually, I’ve had to reboot the machine, because the zpool doesn’t appear accessible any longer. After reboot, the pool appears fine, no faults, and I can resume rsync for a while.
EDIT: Of note, the rsync process seems to stall and I can’t get it to respect SIGINT or Ctrl+C. I can SSH in separately and running zpool status hangs with no output.
While the workaround seems to be partially successful, the point of using rsync is to make it fairly hands-free and it’s been a week long process to copy the 3TB that I have now. I don’t think my zpool should be disappearing like that! Makes me nervous about the long-term viability. I don’t think I’m ready to drop down on Unraid.
rsync is being initiated from the NAS to copy from the old server, am I better off “pushing” than “pulling”? I can’t imagine it’d make much difference.
Could my drives be bad? How could I tell? They’re attached to a 10 port SATA card, could that be defective? How would I tell?
Thanks for any help! I’ve dabbled in linux for a long time, but I’m far from proficient, so I don’t really know the intricacies of dmesg et al.
I don’t have practical experience with ZFS, but my understanding is that it uses RAM a lot… if that’s new, it might be worth checking the RAM by booting up memtest (for example) and just ruling that out.
Maybe also worth watching the system with
nmonorhtop(running in anothertmux/screenpane) at the beginning of the next session, then when you think it’s jammed up, see what looks different…Awesome, thanks for giving some clues. It’s a new build, but I didn’t focus hugely on RAM, I think it’s only 32GB. I’ll try this out.
Edit: I did some reading about L2ARC, so pending some of these tests, I’m planning to get up to 64gb ram and then extend with an l2arc SSD, assuming no other hardware errors.
Based on this thread it’s the deduplication that requires a lot of RAM.
See also: https://wiki.freebsd.org/ZFSTuningGuide
Edit: from my understand the pool shouldn’t become inaccessible tho and only get slow. So there might be another issue.
Edit2: here’s a guide to check whether your system is limited by zfs’ memory consumption: https://github.com/openzfs/zfs/issues/10251
Just another thought… Maybe just format the drives as a massive EXT4 JBOD (just for a temp test) and copy the data again - just to see if ZFS is the problem… maybe it’s something else altogether? Maybe - and I hope not - the USB source drive is failing after long reads?
I believe there’s another issue. ZFS has been using nearly all RAM (which is fine, I only need RAM for system and ZFS anyway, there’s nothing else running on this box), but I was pretty convinced while I was looking that I don’t have dedup turned on. Thanks for your suggestions and links!