There's been some discussion over on the SQL Server Central forums about database mirroring performance, and one question in particular on how to do index rebuilds on mirrored VLDBs. Remember that in database mirroring, the database has to be in the full recovery mode, so all index rebuilds are fully logged . It all comes down to the amount of transaction log generated and whether this causes a problem. In synchronous mirroring, the additional log being generated could overload the network link between...(
read more)
Read the complete post at http://www.sqlskills.com/blogs/paul/2007/10/19/MoreOnDatabaseMirroringPerformanceAndIndexMaintenance.aspx