Request for help troubleshooting FreeBSD 11.3-RELEASE-p5 panic

[David Christensen]

freebsd-questions:

I have a Dell PowerEdge T30:

2020-01-07 19:50:20 toor at soho ~
# freebsd-version
11.3-RELEASE-p5

2020-01-07 19:50:40 toor at soho ~
# uname -a
FreeBSD soho.tracy.holgerdanske.com 11.3-RELEASE-p5 FreeBSD 
11.3-RELEASE-p5 #0: Tue Nov 12 08:59:04 UTC 2019 
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64


This machine (soho) previously ran FreeBSD 11.2 RELEASE.  I created a 
ZFS pool using 11.2 and put several filesystems on it.


Following end of support for 11.2 around Halloween, I built another 
machine (soho2) with FreeBSD 11.3 RELEASE and created a ZFS pool using 
11.3.  I replicated the filesystems from soho to soho2, migrated 
services, and shelved soho.


Last month, I put a blank system drive in soho and installed FreeBSD 
11.3 RELEASE.  I have noted messages about the previously existing ZFS pool:

2020-01-07 19:56:38 toor at soho ~
# zpool status p1
   pool: p1
  state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
	still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
	the pool may no longer be accessible by software that does not support
	the features. See zpool-features(7) for details.
   scan: scrub repaired 0 in 0 days 02:29:34 with 0 errors on Sun Aug 18 
14:59:03 2019
config:

	NAME             STATE     READ WRITE CKSUM
	p1               ONLINE       0     0     0
	  mirror-0       ONLINE       0     0     0
	    gpt/p1a.eli  ONLINE       0     0     0
	    gpt/p1b.eli  ONLINE       0     0     0

errors: No known data errors


One of the drives in soho2 has failed, so I am now trying to replicate 
the filesystems from soho2 back into soho.  Replication works for 
smaller snapshots, but larger snapshots that take ~10 minutes or more 
cause a panic and reboot.  /var/log/messages from today has some examples:

http://holgerdanske.com/pub/dpchrist/issue/freebsd-11.3/20200107-panic/var-log-messages.log


How do I troubleshoot this?


TIA,


David