Understanding persistent storage

[Per Buer]

On Tue, Apr 19, 2011 at 6:44 PM, Yang Zhang <yanghatespam at gmail.com> wrote:
>
> What I found last time was:
>
> (1) Fetch a page. Miss first time, hit subsequent times.
>
> (2) Restart Varnish.
>
> (3) Fetch same page. Miss.

Right. This is actually valid behavior. The goal of the persistent
storage isn't to salvage _all_ of the data across a restart, only to
salvage _most_ of the data. Salvaging all of the data would require
database type storage semantics which is more or less impossible to
achieve without scarifying a lot of persistence.

As -spersistent is implemented, the storage silo which is open at the
time of the crash/restart is discarded completely, so most of the
objects inserted into the cache the last few seconds before the crash
will  certainly be lost. Remember, we're a cache, not a data store.

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