[EMAIL PROTECTED] wrote:
> what does "clustered qmail solution " mean...
It means "multiple systems acting as a single system". For example,
"aol.com" is not a single, huge 25,000 horsepower server box that
handles all of AOL's incoming mail. Instead, "aol.com" points to a
list of mail exchangers (MX's), any of which will accept mail for
addresses at aol.com. When AOL needs additional incoming SMTP
capacity, they can either add new entries to their MX record, or they
can upgrade existing systems. Since there are many of them, if one
breaks or is down for upgrading or patching, their mail still works.
It's also possible to cluster POP and IMAP servers, either with
partitioned or shared responsibilities. E.g., you could have two POP
servers: one for users whose names start with the letters A-M and
another for those starting with N-Z. That spreads the load, but
doesn't provide redundancy: if a server is down, some users are unable
to access their mail. Alternatively, you can have multiple POP servers
accessing a shared high-availability mail store like a
network-attached RAID. The RAID is still a single-point-of-failure,
but it's designed to minimize downtime. qmail's maildir format is
especially well suited to storage on a network-attached RAID since it
avoids messy locking problems.
-Dave
