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Re: ext3 and chattr +S on postfix spools

Andrew Morton:
> Still.  Please: what are the requirements for MTAs, and for
> postfix?

The general requirement is that the machine not lose mail, regardless
of when it crashes. 

More specifically:

The only excuse for losing mail is physical damage.

open() implements O_CREAT|O_EXCL correctly.

fsync(fd) guarantees no loss of file content or pathname information.
close() after fsync() is not allowed to break this guarantee.

rename() and link() are synchronous. Some applications also demand
that the operations be atomic.

rename() is safe: it never loses pathname information no matter
when the operation is interrupted, and no matter why it fails.

An operation that succeeds never reports failure. That is, no NFS
garbage with non-idempotent operations.

Postfix does not promise reliable operation over networked file
systems, thus it has no requirements for network file systems.

Time's up. I have a full-day class and conference next week that
requires some preparations.


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