November 7, 2003 at 9:27 am
Hi all, I know Replication is not meant to be a high availability/dr solution, but if Enterprise Ed is not available to us, that means we can't log ship easilly. So can replication be used to maintain a hot spare site? More directly, when/if my publisher crashes, will my subscriber database be able to function as a standalone? I would have 2 servers one a publisher in one building and one a subscriber in another building, doing transaction replication every hour or so. Thanks in advance!
November 7, 2003 at 5:34 pm
First, I know of nothing that keeps you from doing log shipping with standard. It's not all packaged up, but the basic SQL 7 scripts that were provided will still do log shipping. We do it all the time.
We use both replication and log shipping.
We use Replication to provide a replica for read/write access (read/only is also possible). It works, it's reasonably fast, but it is not a spare in the same sense. The replica is not really a replacement for the original. If the publisher goes down, the subscriber (in most cases) can be used for a long time, and when the publisher restored it will synchronize. However, if the publisher is literally lost, I think you are screwed. You could probably salvage the data if done carefully, but I'm not aware of a way to turn a subscriber back into an original publisher database as a form of recovery. In fact, of course, the subscriber may not be at all a complete copy.
Log shipping on the other hand does not provide a reliable general purpose replica. By that I mean that if you are actively doing log shipping you cannot access the database -- access and recovery of the log files conflict. It is possible to do so in a limited fashion, for example you could have it available 23 hours a day, then recover shipped logs 1 hour, provided you are happy being 23 hours behind.
And log shipping provides only a read-only "replica" if you do work around the above.
I find log shipping the best way to maintain a hot standby.
I find replication the best way to maintain either a read only, or read-write copy for simultaneous access.
And finally a closing comment -- we frequently do a third brute force approach, shut down and detach a database, and simply make copies of it as a way to get copies for read only use. An on-line backup adn restore can do the same (but requires all that intermediate space and time).
November 17, 2003 at 1:59 pm
Thank you very much for the info!
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