February 10, 2009 at 6:38 pm
Hello DBA Gurus...
I'm in the process of setting up mirroring on a fairly large db (100+GB) and was wondering what kind of caveats to look out for.
Thanks
Dave
February 10, 2009 at 10:04 pm
Database size isn't relevant. It's # of transactions that have to be sent from one to the other that create the load.
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February 10, 2009 at 10:22 pm
Steve Jones - Editor (2/10/2009)
Database size isn't relevant. It's # of transactions that have to be sent from one to the other that create the load.
That being said... Does the primary server ever suffer do to the connection to the mirrored server? Will the primary servers performance degrade if the the transactions are slow going to the mirrored server?
February 10, 2009 at 10:27 pm
What do you mean by suffer? Slow down because of load?
You transfer over log records, and that takes some overhead. Not much, very little, but there is some slight overhead to the copying of the log records.
Also, if the log records can't be delivered, the log on the primary can't be cleared, so that can be an issue.
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February 11, 2009 at 12:27 am
I would say bandwidth is a critical factor here.
February 11, 2009 at 2:19 am
That being said... Does the primary server ever suffer do to the connection to the mirrored server? Will the primary servers performance degrade if the the transactions are slow going to the mirrored server?
What type of configuration are you trying to set up for mirror?
high Availability
high performance
high protection
February 12, 2009 at 7:00 am
We mirror a 450 GB database and I see no ill effects. If the connecton is broken between the primary and secondary server, the log is still backed up on the primary as scheduled. Whenever the secondary is available the logs will start transferring again. The Network seems to be the only cause of an occasional bottleneck at our shop.
February 12, 2009 at 7:28 am
As mentioned above, it is the number of transactions that will be the issue. We mirror a 700++ GB database to a remote location and it usually is between 40 - 180 KB/s for the Restore Rate. The Unrestored log is 99% of the time at 0KB and every once in a while it is at 1 KB... so unless you have a really crappy connection to your mirror, you shouldn't have issues. We use the High Performance model.
February 12, 2009 at 6:28 pm
It sounds like we're going to be fine. Both servers have fiber cards and are on the same physical switch. Transactions/sec are < 300.
Thanks!
February 12, 2009 at 6:35 pm
Use sp_dbmmonitorresults stored proc to see the send rate. If send rate is good, then you should not have problem with network bandwidth.
If you have are mirroring highly transactional database, better go for asynchronous mode..
--Sudhie.
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