Varnish restarting sporadically... losing entire cache...

[Ben Nowacky]

Hoping someone can help... We're just trying to roll out varnish to a
somewhat large production site (30million monthly pageviews). Things seem to
be working, hitting about a 90% hitrate so far. Using Wordpress for a CMS
and standard LAMP stack on the back-end.

- Deployed varnish on 1 of our servers yesterday for final testing on the
live site. Runs along well, seems to be doing great. Run varnishstat to keep
an eye on it, and randomly all the stats reset back to 0, and there's a full
cache purge, which means i'm guessing varnish has restarted?

I can't, for the life of me, figure out why it's been restarting. I've
tweeked settings that I've seen recommendations for, upped cache/thread/etc
an still seems to be happening.  Not sure if anyone else has seen this
behavior or not, but if anyone has any suggestions for troubleshooting, or
figuring out what's going on, would appreciate any help ! I've got varnish
running with persistence now, so it's helping a bit when there's a restart
since it's not completely unprimed, but need to figure out the cause of the
instability.

Any help would be awesome... Thanks !