Understanding persistent storage

[Yang Zhang]

I've been playing around with the experimental persistent storage in
varnish-2.1.5 SVN 0843d7a, but I'm finding that the cache doesn't seem
to survive across restarts.

This matches up with hints like "When storage is full, Varnish should
restart, cleaning storage" from
http://www.varnish-cache.org/trac/wiki/changelog_2.0.6-2.1.0.

Can anyone clarify what's persistent about persistent storage, how it
differs from -sfile, etc.? I tried looking up info but didn't find
much beyond implementation details in
http://www.varnish-cache.org/trac/wiki/ArchitecturePersistentStorage.
Thanks in advance.

-- 
Yang Zhang
http://yz.mit.edu/