Database Mirroring: Farewell, But Not Goodbye

The November 7 launch of SQL Server 2005 is right around the corner and the SQL Server 2005 September Community Technology Preview (CTP) released last week is the last scheduled CTP before the big balloon drop. I'll share some housekeeping comments about the September CTP in a moment, but first I wanted to discuss the most important news that came with the CTP's release. As you might have heard, SQL Server Express Manager isn't part of the September CTP, but will be released post-release to manufacturing (RTM); Database Mirroring won't be supported in the SQL Server 2005 RTM, although it's still part of the September CTP.

Express Manager is a new administrative GUI for SQL Server Express, the new SQL Server edition that's replacing MSDE. Although I'll miss seeing Express Manager at RTM, this news probably won't affect you unless you're already a big MSDE user and plan to upgrade quickly. However, the removal of Database Mirroring is a disappointment, and I know that Microsoft is disappointed as well.

Database Mirroring, a much anticipated feature for high-availability and disaster-recovery planning, is valuable for business-continuance strategies in co-located server-hosting environments over wide distances. Microsoft admitted that the feature simply isn't delivering the performance required for the uber-high-end environments in which Database Mirroring would be most needed. Here's what Microsoft has to say on the matter:

"Our goal throughout the development of SQL Server 2005 has been to deliver a release that is high quality and meets our customers' most demanding business scenarios," said Ilya Bukshteyn, director of communications for SQL Server at Microsoft. "For this reason, we've made the decision to extend the feedback cycle for Database Mirroring. We want more validation from customers to ensure that Database Mirroring doesn't just support 99.99 percent of customer workloads, but that it can be relied upon for the remaining .01 percent as well."

If you'd like the complete rundown about the September CTP from Microsoft Senior Vice President of Server Applications Paul Flessner, you can read his public letter at .

It's important to note that Microsoft is positioning the removal of Database Mirroring as a delay, not an abandonment of the feature. Microsoft says that Database Mirroring will ship sometime in the first half of 2006, but won't go on record with a specific date. In addition, the feature will be available through a trace flag in the RTM. However, this trace flag is intended solely for evaluation purposes and isn't supported in production environments unless you're part of the Microsoft GoLive program for SQL Server, which lets early adopters go into production with pre-release software.

What's the net effect? It's hard to say. Realistically, not many customers need database mirroring. However, a small subset of customers was anxiously waiting on this feature, and from a marketing and mind share perspective, it puts Microsoft at a disadvantage in comparison with key enterprise database competitors such as Oracle and IBM DB2.

You can find the complete rundown of September CTP features and order the SQL Server Readiness Kit CD at .

Finally, I'd like to note the divergence in naming standards that the SQL Server and Visual Studio teams are using. For the past few months, both groups have released Community Technology Previews (CTPs). The latest SQL Server release is still called a CTP, but the latest Visual Studio 2005 release is called a Release Candidate (RC). The SQL Server 2005 September CTP and the Visual Studio 2005 RC are compatible with each other. Why the name-change? Beats me, but as Bill (Shakespeare not Gates) might have said, "A rose by any other name is still just a beta."

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