Network Computing is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Microsoft Pushes SQL Server Toward Continuous Hot Availability

Data mirroring, the ability to generate an up-to-the-second mirror image of an operational database, will become part of Microsoft SQL Server 2005 as Microsoft released Service Pack 1 for its database Wednesday.

Data mirroring is an option with the Oracle database and IBM's DB2 database. SQL Server's Service Pack 1, as previously announced, pushes the Microsoft system onto the same high-availability playing field as its competitors.

SQL Server 2005 already includes such continuous-operation features as the ability to take database snapshots, which allows the reconstruction of the database at a previous point in time. Some database users, for example, record a snapshot every hour. Its predecessor, SQL Server 2000, had the ability to "fail over" from one server to another in a cluster, avoiding downtime due to a hardware failure.

But the data mirroring feature comes closer to the "continuous availability" goal set by Microsoft Senior VP Paul Flessner earlier this month. Data mirroring "is a milestone in support of that vision," says Carol Dullmeyer, Microsoft senior product manager.

With mirroring, two servers are linked together, each creating the same log of events from a stream of transactions. Mirroring software also listens for the "heartbeat" of the primary server. If it detects an outage, within a few seconds the backup copy of the data will become the primary database server, picking up where the other left off, Dullmeyer explains.

  • 1