On Wed, 8 Nov 2006, [EMAIL PROTECTED] wrote:
> Unlike the NFS monolith, we have no single point of failure that loses the
> entire IMAP service. The worst case scenario is that a small percentage
> of the user community is temporarily (a matter of minutes) offline while
> we deploy a replacement.
A quick procedure question - how do you do this? I understand how
you spread users across servers via DNS, etc., but what happens to the data
of users on that down server? Assuming it's more that a simple hang/ reboot
problem, do you move the hard drives to the replacement system, share via
SAN, reload from backup, etc?
We do a combination of all of the above.
Also, approximately how many servers do you
have for your 80,000 (?) email users.
I don't know. It's a lot fewer than it used to be, thanks to replacing
the AIX RS/6000 machines with modern Linux machines.
And how does an organization phase from a "mail.lehigh.edu" to
"user.m.lehigh.edu" structure without a lot of pain? It would have been
simple 8 years ago with <100 IMAP users. Now...
That's more of an administrative question than a technical one. We
recognized early on that "mail.washington.edu" wasn't going to work, and
that went away with the NFS based facility.
It's been a long while, but I recall that we had a transition period. We
were helped a great deal by the fact that many of our users were UNIX
shell users, and thus we were able to reconfigure the users for them.
Similarly, many of our Windows users run centrally-managed systems, and
those also could be reconfigured by us. So the impacted users were the
subset who had to reconfigure themselves.
I don't recall it being particularly controversial. The new naming system
was easy to explain, and the benefits of a faster and more reliable mail
server were clear.
In my opinion, users will accept change if they perceive a benefit. The
corrolary is that they will resist change if they perceive no or negative
benefit.
The benefits of switching from traditional UNIX mailbox format are huge.
IMAP suddenly becomes much faster, and multiple shared access works. If
you haven't experienced the difference, you will be amazed.
Multiple shared access may not sound important, until you realize that
most IMAP clients (Pine being the notable exception) routinely spawn off
multiple sessions to the same mailbox.
With traditional UNIX format and no NFS, the new session kills the
previous session.
With traditional UNIX format and NFS, the sessions play "spin the roulette
wheel" and hope that in the case of conflict the impacted session will
realize it in time and kill itself rather than corrupt the mailbox. As in
routine, there is the one slot on the wheel where all the players lose.
-- Mark --
http://panda.com/mrc
Democracy is two wolves and a sheep deciding what to eat for lunch.
Liberty is a well-armed sheep contesting the vote.
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