Multiple Mirrors

, 2010-11-30

Up through SQL Server 2008 R2 database mirroring has been limited to a single mirror for each database. While that does work well for many companies, as you become larger and more dependent on your computer systems, there is a need to have multiple mirrors.

Often someone wants to failover to another database on the same network for capacity reasons if there are minor issues. Moving all clients to a secondary data center is not something you always want to do, especially as the secondary data center might not include the same level of bandwidth and may cost more.

HADR

In SQL 11, there is work underway to implement HADR, high availability and disaster recovery, which is an enhanced database mirroring. In this new technology, multiple mirrors are possible, allowing you to have multiple up to date copies of your data in separate locations. These are now called “replicas” and you get up to 4, according to Brent Ozar (HADRON Rocks). I didn’t see that listed, but I’m sure Brent knows more about this stuff than I do.

The other nice things is that you can failover multiple databases together, which you put in an “availability group” and configure together. This is good since many applications might require multiple databases, and it could be important that all databases move to the same server at the same time.

Overall this is cool, and I am looking forward to this technology being deployed. Only one replica works in CTP1, so we can’t really see this working, but it could be an amazing edition to your DR strategy in the future. One note is that this is built on Windows clustering, which no longer requires shared storage, but might require Enterprise Edition, so that will limit how widely this is deployed.

I’ll write more on this later, but the ability to have multiple mirrors, and have multiple databases failover as a group, is something that DBAs should look forward to.

Rate

Share

Share

Rate

Related content

Database Mirroring FAQ: Can a 2008 SQL instance be used as the witness for a 2005 database mirroring setup?

Question: Can a 2008 SQL instance be used as the witness for a 2005 database mirroring setup? This question was sent to me via email. My reply follows. Can a 2008 SQL instance be used as the witness for a 2005 database mirroring setup? Databases to be mirrored are currently running on 2005 SQL instances but will be upgraded to 2008 SQL in the near future.

2009-02-23

1,567 reads

Networking - Part 4

You may want to read Part 1 , Part 2 , and Part 3 before continuing. This time around I'd like to talk about social networking. We'll start with social networking. Facebook, MySpace, and Twitter are all good examples of using technology to let...

2009-02-17

1,530 reads

Speaking at Community Events - More Thoughts

Last week I posted Speaking at Community Events - Time to Raise the Bar?, a first cut at talking about to what degree we should require experience for speakers at events like SQLSaturday as well as when it might be appropriate to add additional focus/limitations on the presentations that are accepted. I've got a few more thoughts on the topic this week, and I look forward to your comments.

2009-02-13

360 reads