Where Squid Keeps Its Cache Digests
Follow a digest from its in-memory lookup copy to the disk-cache item exchanged with neighbours.
Both RAM and disk are involved. Squid uses a Cache Digest in memory when deciding whether a neighbour might have an object; the disk copy supports storage and exchange.
| Digest | Lifecycle described by Squid's Cache Digests FAQ |
|---|---|
| Locally generated | Built and retained in RAM, then written to disk as an ordinary cache item that neighbours can request over HTTP. |
| Fetched from a peer | Kept in RAM for fast lookup and stored on disk for reuse after restart and distribution to neighbours. |
These are summaries of cache contents, not copies of the cached response bodies. When accounting for storage, distinguish the local summary, downloaded peer summaries and actual cached objects.
A positive lookup also is not a guarantee that the peer can serve the object. Digest membership can produce a false hit, so Squid may ask a peer that cannot satisfy that request.