Advantages of TSM DB,LOG mirror in TSM than Hardware,OS level mirrors

tsmsupport

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PREDATAR Control23

Hi,



I would like to know are there any advantages by doing TSM level mirroring rather than Hardware or O/S level mirrors.





Thanks

TSMsupport
 
PREDATAR Control23

I'd say TSM mirroring is better because hardware mirroring doesn't protect against software faults.



We've got a single copy of the database and log volumes on a very reliable RAID. However, something, either TSM or the OS, corrupted one of the database volumes. The RAID doesn't care- it's garbage-in, garbage-out. By mirroring at the application level, you get some checking (AFAICT) by TSM to make sure that things are consistent.



You can (with roll-forward) also recover single database volumes from a mirror.



Personally, I'd suggest TSM mirroring. That's the way we'll be going from now on.



HTH.
 
PREDATAR Control23

Hi SPARKY,



i think your suggestions are pretty good.



Can u please tell me about (AFAICT) i mean how can we perform this.



Thanks

TSM support
 
PREDATAR Control23

Oh, sorry. AFAICT is an acronym... "As Far As I Can Tell", refering to my own ignorance regarding the specific mechanisms TSM uses for verifying consistency and validity of mirrors.



Once the mirrors are set up, the state of the mirrors can be checked with "q dbvol" and "q logvol".



Sorry for the confusion.
 
PREDATAR Control23

If you have enterprise class SAN Array, do you think still the TSM mirroring needed?



I think that will add the load to the TSM server.
 
PREDATAR Control23

TSM Mirroring provide a much better protection then just simple h/w mirroring. The impact on performance is very limited & now day the server is powerful enough to do it all



Good luck



HP
 
PREDATAR Control23

TSM mirroring is the preferred method of mirroring. If you were to have something corrupt your log file, tsm would bring that volume offline, send an error message, and continue working.



With the TSM db mirrored via TSM, you can, in certain situations, actually get a peformance increase, as queries could be made against EITHER of the TSM database's.



you need to ensure that the mirror volumes are not on the same drives (I see that a lot) and that they are not on the same controller. :)





:grin:
 
PREDATAR Control23

Shoot if ya got the money put them on seperate FastT's and then life is beautiful. Oh and my personal opinion is use RAW when you can (of course that only works on Unix and no I don't think its supported on Linux).
 
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