FreeLists / oracle-l / Re: ASM mirroring, which is good?

[Andreas Piesk <a.piesk@xxxxxxx>]

Syed Jaffar Hussain schrieb:
>  
> We have recently implemented 2 node RAC on AIX, with ASM defined 
> external redudancy option.
>  
> We didn't come across of any performance problems with this 
> option. However, I would like hear from any of you about the performance 
> difference setting external or normal/high redudancy configuration with ASM.
>  
i implemented a systems with two 2-node-RACs with Dataguard as 
replication solution. each RAC uses ASM with normal redundancy to mirror 
the data between 2 independent storage boxes. the storage boxes itself 
uses RAID-10 to mirror the data. Oracle version is 10.2.0.2 on AIX.
performancewise i'm quite satisfied. during backup tests i was able to 
achieve max. 800MB/s per RAC. redo is applied at max. 150MB/s per node, 
usually at 50-75MB/s. i put the redologs on ASM but to get the best 
performance i would recommend using RAW devices for all redologs.
writing to only one storagebox results in slightly better throughput 
(approx +5-10MB/s).
so ASM works well in terms of performance and stability with three 
exceptions:
1. don't let a complete failuregroup die if you have only two, better 
have three.
2. always have a free ASM disk available, otherwise rebalancing may not 
work.
3. writing to ASM seems to hang ocassionally for several hundred 
milliseconds, reason unknown.

regards,
-ap

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