On 07/01/2012 11:16 PM, Maxwell Smart wrote:
On 07/01/2012 07:59 PM, Eric Shubert wrote:
On 07/01/2012 07:47 PM, Maxwell Smart wrote:
Rsync is appropriate for backing up mail stores and configurations
(mysql database needs to be addressed separately). I don't see it
playing a role in HA configurations, except for providing backups,
which should still be done. HA, like raid, is *not* a backup solution.
I fail to understand why two identical servers in separate locations
doesn't qualify as a backup solution. Both servers have secondary
backup hard drives with duplicated data and the second server takes the
place of the first if the first is ever broken. Why is that not
desirable?
I didn't say that's not desirable. I said it is not a backup solution.
As soon as the second server takes the place of the first, where's
your backup?
I am curious, what would you do?
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I don't have a requirement for the highest level of availability. My
users can get along without access to email for a couple hours
(occasionally, not regularly), so I don't have a hot spare with their
emails stored on it. That'd be nice of course, but it's just not worth
the time and effort setting it up and maintaining it. The production
host is reliable enough that it provides sufficient availability. I do
have a backup MX which can receive and relay incoming messages in the
event that the primary goes down. This merely provides quicker access to
messages which would be sent while the primary is down, and is not very
critical. Sending servers will typically keep messages in their queue
for 12+ hours (which I personally think is excessive).
I backup user and configuration data to a raid-1 mirror which is at a
separate location, using rsync that runs as a cron job. The backup
datasets never go live. They're only used for disaster recovery, and
occasionally (but more often) when a user inadvertently deletes a mail
folder or messages. Backups should provide this type of recoverability,
which HA setups do not do on their own. Hence, HA is not a backup solution.
--
-Eric 'shubes'
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