Mailinglist Archive: opensuse (1695 mails)

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Re: [opensuse] 10.2 no RAID to 11.0 RAID 1
  • From: G T Smith <grahamsmith@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
  • Date: Wed, 24 Sep 2008 09:00:12 +0100
  • Message-id: <48D9F38C.1000104@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
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Carlos E. R. wrote:


The Tuesday 2008-09-23 at 17:40 +0200, Hylton Conacher (ZR1HPC) wrote:

I guess the way around that is to have two rsync jobs being one for
the mail directories and the other for only the document directories?

Or more frequent backups. Those are the cases where raid does not
help: both
copies of the document wold be broken.

Restoring email queues is not so simple, anyway, maybe you could end
resending mail already sent. I think that often it is better to leave
the
email as lost and resend from the client if needed. This is a
situation for
which RAID is better, IMO.

A different thing would be a pop/imap server.
What would be different?

A sending smtp server does not stores many emails, they are sent as soon
as possible. There is almost no point in backup.

A receiving server can store millions of emails.

I ask as it is actually a one person IMAP
Dovecot, Postfix,SpamAssassin, Procamil mailserver store I aim to
setup. The main purpose of the mail server is to lose as little email,
if any email, at all. How can I ensure that no received mail since the
last mirror/backup is not lost? Resending email already sent is fine,
losing email already received is unacceptable as I will not know who
to ask to resend?

Then the alternative is to store every email, as soon as it arrives, on
two disks or servers. Notice that, as both are running continuosly, any
of them could break as often as the other.

-- Cheers,
Carlos E. R.

This is where procmail has it uses... a procmail recipe to forward
incoming mail to a mail location or secondary mail server should have a
good chance of duplicating the majority of incoming mail.

However, it should also be noted *no* backup system will be guaranteed
to be 100%, it is more of the decision of how close to that 100% one can
reliably get. This is a basic cost benefit analysis, weighing the costs
of the backup regime against costs of either loosing or recovering any
damaged data, YMMV. (Using RAID in itself is *not* really a backup
mechanism, it provides performance and continuity of service but that is
a different issue).

Email by its nature presents special problems, the dynamic nature of the
data structure makes it highly probable that things will be missed
during backup (unless you shutdown the mail system, backup the data and
restart, data gaps are inevitable... and for most multi-user scenarios
such a backup regime would be unacceptable and also probably
impracticable). As any backup regime is only as good as its restore
mechanism, and restoring email can be highly problematic, people can
come to their own conclusions.

BTW Anyone who claims that they have never lost data, is probably being
rather naive. They have lost data but they just do not know it (yet),
and if they did not know it they probably did not need it anyway :-)

- --
==============================================================================
I have always wished that my computer would be as easy to use as my
telephone.
My wish has come true. I no longer know how to use my telephone.

Bjarne Stroustrup
==============================================================================
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