On Thu, 2004-07-08 at 22:25, Mark Crispin wrote: > Each user has his own DNS name for his server. In my case, it is > mrc.deskmail.washington.edu, and that is the only system that I connect > to. Some number of users are on the same physical CPU. mrc.deskmail is > currently on a machine called mailer52. mailer52 is also the ???.deskmail > for other users.
Doesn't that mean that a user is located only in a single server, so in case it breaks, the user can't read mail until admin has fixed the problem by restoring mails from backups and moved the accounts to new server? Unless the account is mirrored between multiple servers in realtime as well (how?), user can also lose mails. Better than everyone's mail breaking, but I'd prefer transparent failovers without any data loss. > The reason for this is that there is more than synchronizing locks. It is > also necessary to synchronize inode status and data. It is a requirement > that a change anywhere in the file be instantaneously (atomicly) reflected > in all other members in the cluster. This requires an *extremely* complex > series of semaphores. As far as I know CFS on TOPS-20 is the *only* > implementation to have gotten it right (although VMS clusters may also > have done so). I'd think there are already many filesystems capable of that, although most probably are commercial. Except recently RedHat released GFS as open source which should be able to do that. > Databases (and mailboxes are a type of database) are part of the 1% that > require 99% of the work. Oracle works with GFS, I bet IMAP server could work with it too.
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