Re: Oracle8 on AIX4.2 - Raw disk or file system?

It's not so much the volume of updates, but frequency and speed requirements, and the nature of the database operations. Another thing to think of is reading, as most (but not all) databases undergo far more read than write activity.

The loss of 'read-ahead' with raw disks can actually make them much slower than file-systems for read-intensive databases with larger block sizes.

More info can be found in Oracle 7 Server Tuning 7.3.3 which comes with the database software (i.e., it's a normal Oracle manual, not an additional Oracle Press book.) See section Chapter 14, Tuning I/O for a comparison of raw v file-system statistics for varying block-sizes and I/O operations.

And, MOST importantly, TEST your own system with realistic data and transactions to confirm that you really are gaining from the use of raw devices v file-system. Even then, alternative technologies (striping, mirroring, RAID) may give you better performance (and recovery and managability) over raw devices.

Just my take.

Steve Phelan (UK)

>Hello Robert,
>
>in the book
>Advanced Oracle Tuning and Administration, Oracle Press, Osborne
>you can read many disadvanteges (ie administration) and
>few advanteges (multiple batch jobs).
>Furthermore:
>"If the majority of your database activity is from online users
>executing small transactions, you will likely see little or no
>performance benefit using raw devices."
>
>
>I cant remember where I heared the following statement:
>"Use raw devices if your updates/inserts are more than
>1 GB daily."
>Perhaps anyone can tell more about this rule...
>
>Stephan Schaefer
>stesch_at_camline.com
>
>
Received on Mon Mar 02 1998 - 00:00:00 CST