Re: Q: Is RAID/striping good with Oracle???

Uday Bikkasani wrote:
>
> Raid 0 Works fine for us and the question that I have is a follow up to
> this topic
>
> is there a particular way that I can arrange the rollbacks, redologs
> and mirrored redo logs to reduce the file i/o bottlenecks on a raid 0.
>

Let me address the redo logs first. Ideally, the redo logs should be on separate spindles from any other files on the system. If you let Oracle mirror them, the mirrored logs should also be isolated. If you can afford it and you really want to optimize your redo logs, you can place each redo log on separate disk. The logic behind this is that while one redo log is being read for archiving (you ARE running in archivelog mode aren't you?), it won't interfere with the current log file that is being written to. If you want to go to this level of optimization, I would use 6 logical drives (each logical drive could consist of two or more drives striped together but I wouldn't do this unless you have a high level of DMLs in your transactions). A configuration with 6 redo log groups would look something like this:

Disk1 - redo01a.log, redo04a.log
Disk2 - redo02a.log, redo05a.log
Disk3 - redo03a.log, redo06a.log
Disk4 - redo01b.log, redo04b.log
Disk5 - redo02b.log, redo05b.log
Disk6 - redo03b.log, redo06b.log

Disks 1-3 should be on a separate controller from disks 4-6. With this configuration, you should be able to size your redo logs and time your archives so that no disk is being accessed for logging and archiving at the same time. Obviously your archivelog destination should be a separate device.

As for rollback tablespaces, if you are only using public rollback segments, put the entire tablespace on one logical drive that is isolated from other files in the system. This logical drive could consist of several physical drives striped together. If you have certain transactions that require lots of rollback activity, you can create separate rollback tablespaces and segments that can be specified for use at the start of the transaction. These special use rollback segments should be physically isolated from the rest of the system.

Of course, it is very expensive to optimize everything to the level I have detailed here. Your job as the DBA is to analyze your needs against your available resources and figure out what will give you the most bang for your buck. I hope this information is helpful in that task.

Vince Received on Fri Aug 23 1996 - 00:00:00 CEST