Just tested, thanks for the suggestion! It killed a few instances of rsync, but there are two apparently stuck open. I issued reboot and the system seemed to hang while waiting for rsync to be killed and failed to unmount the zpool.
Syslog errors:
<span style="color:#323232;">Dec 31 16:53:34 halnas kernel: [54537.789982] #PF: error_code(0x0002) - not-present page
</span><span style="color:#323232;">Jan 1 12:57:19 halnas systemd[1]: Condition check resulted in Process error reports when automatic reporting is enabled (file watch) being skipped.
</span><span style="color:#323232;">Jan 1 12:57:19 halnas systemd[1]: Condition check resulted in Process error reports when automatic reporting is enabled (timer based) being skipped.
</span><span style="color:#323232;">Jan 1 12:57:19 halnas kernel: [ 1.119609] pcieport 0000:00:1b.0: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
</span><span style="color:#323232;">Jan 1 12:57:19 halnas kernel: [ 1.120020] pcieport 0000:00:1d.2: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
</span><span style="color:#323232;">Jan 1 12:57:19 halnas kernel: [ 1.120315] pcieport 0000:00:1d.3: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
</span><span style="color:#323232;">Jan 1 22:59:08 halnas kernel: [ 1.119415] pcieport 0000:00:1b.0: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
</span><span style="color:#323232;">Jan 1 22:59:08 halnas kernel: [ 1.119814] pcieport 0000:00:1d.2: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
</span><span style="color:#323232;">Jan 1 22:59:08 halnas kernel: [ 1.120112] pcieport 0000:00:1d.3: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
</span><span style="color:#323232;">Jan 1 22:59:08 halnas systemd[1]: Condition check resulted in Process error reports when automatic reporting is enabled (file watch) being skipped.
</span><span style="color:#323232;">Jan 1 22:59:08 halnas systemd[1]: Condition check resulted in Process error reports when automatic reporting is enabled (timer based) being skipped.
</span><span style="color:#323232;">Jan 2 02:23:18 halnas kernel: [12293.792282] gdbus[2809399]: segfault at 7ff71a8272e8 ip 00007ff7186f8045 sp 00007fffd5088de0 error 4 in libgio-2.0.so.0.7200.4[7ff718688000+111000]
</span><span style="color:#323232;">Jan 2 02:23:22 halnas kernel: [12297.315463] unattended-upgr[2810494]: segfault at 7f4c1e8552e8 ip 00007f4c1c726045 sp 00007ffd1b866230 error 4 in libgio-2.0.so.0.7200.4[7f4c1c6b6000+111000]
</span><span style="color:#323232;">Jan 2 03:46:29 halnas kernel: [17284.221594] #PF: error_code(0x0002) - not-present page
</span><span style="color:#323232;">Jan 2 06:09:50 halnas kernel: [25885.115060] unattended-upgr[4109474]: segfault at 7faa356252e8 ip 00007faa334f6045 sp 00007ffefed011a0 error 4 in libgio-2.0.so.0.7200.4[7faa33486000+111000]
</span><span style="color:#323232;">Jan 2 07:07:53 halnas kernel: [29368.241593] unattended-upgr[4109637]: segfault at 7f73f756c2e8 ip 00007f73f543d045 sp 00007ffc61f04ea0 error 4 in libgio-2.0.so.0.7200.4[7f73f53cd000+111000]
</span><span style="color:#323232;">Jan 2 09:12:52 halnas kernel: [36867.632220] pool-fwupdmgr[4109819]: segfault at 7fcf244832e8 ip 00007fcf22354045 sp 00007fcf1dc00770 error 4 in libgio-2.0.so.0.7200.4[7fcf222e4000+111000]
</span><span style="color:#323232;">Jan 2 12:37:50 halnas kernel: [49165.218100] #PF: error_code(0x0002) - not-present page
</span><span style="color:#323232;">Jan 2 19:57:53 halnas kernel: [75568.443218] unattended-upgr[4110958]: segfault at 7fc4cab112e8 ip 00007fc4c89e2045 sp 00007fffb4ae2d90 error 4 in libgio-2.0.so.0.7200.4[7fc4c8972000+111000]
</span><span style="color:#323232;">Jan 3 00:54:51 halnas snapd[1367]: stateengine.go:149: state ensure error: Post "https://api.snapcraft.io/v2/snaps/refresh": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
</span>