Re: [9fans] Anyone working on new upas/fs?

["Russ Cox" <rsc@swtch.com>]

> I've got some heartburn about upas/fs.  Seems our
> user base is growing larger than main memories of our
> imap servers.  Anyone have any ideas to keep systems from
> running out of memory?  Anyone using something that
> virtual memory to keep the mail boxes?

Plan9ports has a new upas/fs (called mailfs for now,
and in $PLAN9/src/cmd/upas/nfs) with only an IMAP
back end, but it demand loads from the IMAP server.
I structured it so that it should not be hard to add a
module for reading local mailboxes too; those could
be loaded on demand as well.  Also, the existence of
the on-demand loading means one can treat memory
as a cache, tossing out messages as memory fills
and reloading them as needed.  One could even keep
a local disk cache of message pieces instead of requerying
a remote mailbox.

The hard part of adding local mailbox support should be
finding your place when the mailbox has changed underfoot,
not any structural part of the fs.

Russ