On Aug 11, 2009, at 2:16 AM, Seth Mattinen wrote:
Show me a clustered filesystem that can guarantee that each file is
stored in at least 3 different data centers and can scale linearly by
simply adding more servers (let's say at least up to thousands).
Easy, AFS. It is known to support tens of thousands of clients [1] and
it's not exactly new. Like supporting the quirks of NFS, the quirks
of a
clustered filesystem could be found and dealt with, too.
I was more thinking about thousands of servers, not clients. Each
server should contribute to the amount of storage you have. Buying
huge storages is more expensive. Also it would be nice if you could
just keep plugging in more servers to get more storage space, disk I/O
and CPU and the system would just automatically reconfigure itself to
take advantage of those. I can't really see any of that happening
easily with AFS.
Key/value databases are hardly a magic bullet for redundancy. You
don't
get 3 copies in different datacenters by simply switching to a
database-style storage.
Some (several?) of them can be somewhat easily configured to support
that. (That's what their web pages say, anyway.)
Clustered filesystems are also complex. They're much more complex
than
what Dovecot really requires.
I mention it because you stated wanting to outsource the storage
portion. The complexity of whatever database engine you choose or
supporting a clustered filesystem (like NFS) is a wash since you're
not
maintaining either one personally.
I also want something that's cheap and easy to scale. Sure, people who
already have NFS/AFS/etc. systems can keep using Dovecot with the
filesystem backends, but I don't think it's the cheapest or easiest
choice. There's a reason why e.g. Amazon S3 isn't running on top of
them.
