Many processes stuck in zfs

[Stefan Bethke]

Over the past couple of months, I've more or less regularly observed machines having more and more processes stuck in the zfs wchan.  The processes never recover from that, and trying to reboot only gets the entire system stuck, without any console messages.  I can enter the debugger, and I have saved a couple of dumps.

The situation seems to be triggered by zfs receive'ing snapshots from the sister machine (both synchronize their active ZFS filesystems to each other, using zfs send and zfs receive).  It appears it's the receiving causing trouble.

Both machines run 8-stable from mid-February, with a single-disk ZFS pool, with ARC limited to 512M, prefetch and ZIL disabled via loader.conf.

What should I be looking at to further diagnose?


Thanks,
Stefan

-- 
Stefan Bethke <stb at lassitu.de>   Fon +49 151 14070811