Re: XP256 Disk Striping for an Oracle 8.1.7 DataWarehouse

"Tom Lewis" <lewis_uk_at_hotmail.com> wrote in message news:6d8d2ec4.0107120349.37cc7615_at_posting.google.com...
> I have a 400GB Oracle 8.1.7 data warehouse deployed onto a XP256. The
> warehouse often needs to full table scan tables of c50GB and uses
> parallel execution to achieve this. The database is using 8K blocks
> and the DB_FILE_MULTIBLOCK_READ_COUNT is set to 16.
>
> The XP256 has been configured with RAID 5 and a stripe size of 256K.
> Its 36 disks have been divided into 8 logical volumes of 4-6 disks
> each with different tables or indexes assigned to each logical volume
> to avoid contention.
>
> I really need some help on two fronts.
>
> What is the optimal relationship between the DB block size and the
> stripe size. Currently, I assume that the database will read 32 blocks
> off disk 1 and then 32 off disk 2 etc. etc. That does not sound very
> parallel to me. Should the stripe size be smaller?

The largest I/O size that Oracle will do with your environment is based on the db_block_size and db_file_multiblock_read_count. max io size = 8k x 16 = 128k.

Ideally, for max throughput, you would want each i/o request to be satisfied by one disk, so the max io size by Oracle should be less than or equal to the stripe width.

There is an outstanding white paper on this topic by Cary Milsap ( http://www.orapub.com/cgi/genesis.cgi?p1=sub&p2=abs107 ).

>
> Secondly, is it necessary to divide the XP256 into different volumes
> for different purposes or is a larger single volume a better approach?

Not exactly sure what you're asking here...

If you're talking about having one large RAID-5 set vs. having several smaller ones, then I vote for several smaller ones. That'll decrease your risk of losing data since you can only afford to lose one disk at a time with
a RAID-5 set.

If you're talking about having one or multiple partitions on an existing RAID-5 set, then I think the only consideration is personal preference.

>
> Many thanks in advance
>
> Tom
Received on Sat Jul 21 2001 - 16:19:25 CDT