NAS unstable, not sure why

[Jon Telfer]

Hi All,
My freenas server has become fairly unstable lately. (HP microserver AMD Turion 54L, 8g RAM, 2x3tb WD RED NAS drives)
Looking at the email and dmesg reports I can see a a kernel panic that appears to reboot the machine. Instability symptoms are that the drive drops off the network and is unreachable at any IP until it has been power cycled, though sometimes it will come back online. Suspicious message I can see in the dmesg output is :

ng_ether_ifnet_arrival_event: can't re-name node epair2b
epair3a: Ethernet address: 02:41:e4:00:0e:0a
epair3b: Ethernet address: 02:41:e4:00:0f:0b
epair3a: link state changed to UP
epair3b: link state changed to UP
epair3a: promiscuous mode enabled
ng_ether_ifnet_arrival_event: can't re-name node epair3b
panic: solaris assert: 0 == bpobj_open(&dle->dle_bpobj, dl->dl_os, za.za_first_integer) (0x0 == 0x2), file: /tank/home/jkh/freenas/FreeBSD/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_deadlist.c, line: 86
cpuid = 0
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a/frame 0xffffff8247e64390
kdb_backtrace() at kdb_backtrace+0x37/frame 0xffffff8247e64450
panic() at panic+0x1ce/frame 0xffffff8247e64550
assfail3() at assfail3+0x29/frame 0xffffff8247e64570
dsl_deadlist_load_tree() at dsl_deadlist_load_tree+0xf3/frame 0xffffff8247e64710
dsl_deadlist_space_range() at dsl_deadlist_space_range+0x83/frame 0xffffff8247e64800
dsl_destroy_snapshot_sync_impl() at dsl_destroy_snapshot_sync_impl+0x556/frame 0xffffff8247e64900
dsl_destroy_snapshot_sync() at dsl_destroy_snapshot_sync+0x51/frame 0xffffff8247e64950
dsl_sync_task_sync() at dsl_sync_task_sync+0x12d/frame 0xffffff8247e64980
dsl_pool_sync() at dsl_pool_sync+0x2af/frame 0xffffff8247e64a00
spa_sync() at spa_sync+0x396/frame 0xffffff8247e64ae0
txg_sync_thread() at txg_sync_thread+0x149/frame 0xffffff8247e64be0
fork_exit() at fork_exit+0x11f/frame 0xffffff8247e64c30
fork_trampoline() at fork_trampoline+0xe/frame 0xffffff8247e64c30
--- trap 0, rip = 0, rsp = 0xffffff8247e64cf0, rbp = 0 ---
KDB: enter: panic
Copyright (c) 1992-2014 The FreeBSD Project.
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The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 9.3-RELEASE-p10 #0 r275790+c9242cc: Sat Mar 14 19:00:55 PDT 2015
root@build3.ixsystems.com:/tank/home/jkh/freenas/objs/os-base/amd64/tank/home/jkh/freenas/FreeBSD/src/sys/FREENAS.amd64 amd64
gcc version 4.2.1 20070831 patched [FreeBSD]
CPU: AMD Turion(tm) II Neo N54L Dual-Core Processor (2196.39-MHz K8-class CPU)
Origin = "AuthenticAMD" Id = 0x100f63 Family = 0x10 Model = 0x6 Stepping = 3

Any thoughts on what the actual issue is and what I can do to fix?

Thanks in advance,
Jon