I have 3*18GB HDs and 9*36GB HDs in RAID 5. I've got high-write enviroment to five tablespaces. What's the best solution for good performance: to have one big partition or five smaller? Or is there no difference for Oracle on RAID 5?
The best solution for a high-write environment is to stay away from RAID 5. RAID 5 introduces a write penalty which can slow your writes down. RAID 3 is better but RAID 1 (or RAID 0+1) is much, much better.
As for which is better, one big partition or five smaller ones, the answer is it all depends. It all depends on how your data is accessed and if you are using RAID in a SAN (or other) environment with a disk cache. With disk caching, it really doesn't make a difference. But without disk caching, it can make some difference. The biggest difference is for your own manageability. The more physical volumes the better to reduce disk contention. And the more logical volumes out of that, the easier it may be for you to separate "hot" database objects.
Without knowing any more about your specific configuration and your data access patterns, I'd say using more logical volumes with RAID 0+1 will be the "best".
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