While I was reviewing one of the sessions from the PASS Community Summit using the streaming media on some new things in SQL Server 2008, I stumbled across a new reason to mirror. The primary reason to mirror of course is availability and to give DBAs that warm fuzzy feeling that another up-to-date (or almost up-to-date if using Async mode) copy of your DB is ready to step into action at a moment's notice. That has not changed in 2008, but another feature was been revealed. It is the "Auto Page Repair" feature. If the Principal encounters a page that is corrupted, it will ask the mirror to send of copy of that page for repair. The mirror is of course replaying the transactions that are sent to it. If the Mirror encounters a problem, it will request a copy of the page from the Principal. This is not a new RAID level, but we could make up a new term like DB-RAID - - ;-) Again, it gives the DBA that warm fuzzy feeling that things will be OK.
Cross-posted from SQLBlog! -
http://www.sqlblog.com