Alot. How much depends on how you're TSM server is configured, but for a large TSM database(+60GB) I would not recommend using serialized database mirroring.
We have a customer running a 220GB TSM database. Using sequential writes wouldnt be an option as the performance loss would be to big. Using sequential mode means TSM will 1st write to one of the copies and after that write to the other copy(if the 1st write was succesful). This means every I/O you make to the TSM database in reality is 2 IO:s the TSM server will have to perform each time. Considering the amount of I/O the TSM server performs, the performance hit will be large. The security risk is mainly in a scenario were TSM writes to both of the db volumes and crashes at the same time. This could result in a partial write = database restore. To avoid this security issue when using parallel writes, enable pageshadowing with "dbpageshadow yes" and "dbpageshadowfile FILENAME". The pageshadowfile should preferable be placed on separate disks from the TSM database volumes. Hope this help Best Regards Daniel Sparrman ----------------------------------- Daniel Sparrman Utvecklingschef Exist i Stockholm AB Propellervägen 6B 183 62 TÄBY Växel: 08 - 754 98 00 Mobil: 070 - 399 27 51 Roger Deschner <[EMAIL PROTECTED]> Sent by: "ADSM: Dist Stor Manager" <[email protected]> 2005-07-30 03:53 Please respond to "ADSM: Dist Stor Manager" <[email protected]> To [email protected] cc Subject mirrorwritedb parallel - tried it? I'm fighting performance problems with a big TSM database, and I was curious if anybody has experience with how much mirrorwritedb parallel could help. More importantly, what are the risks? Roger Deschner University of Illinois at Chicago [EMAIL PROTECTED] ============ "In theory, theory and practice are the same, ============= ========= but in practice, theory and practice are different." =========
