Re: ASM mirroring, which is good?

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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