Re: disk i/o balancing

From: Joseph Thvedt <jthvedt_at_brookings.net>
Date: 1997/02/06
Message-ID: <32FA53B9.7E9C@brookings.net>#1/1

Thanks. I have a couple of questions & comments:

Greg Burris wrote:
[ Joseph wrote: ]
> > redo logs will probably be duplexed by the RDBMS
> > onto multiple plain old drives. Of course, tables & indexes will be
> > separate.
>
> Since you have mirroring in the picture, don't duplex them in Oracle. Let
> the OS/LVM handle the task for you. This will shorten the code path for
> the redo I/O and speed things up slightly.
>

If you mean the redo logs; yes, we'd do either one OR the other, not both.

> I would opt for somewhat of a compromise. Build stripes over 4-8 disks,
> and create a number of small file systems or logical volumes over these
> stripes. Use as many controllers as feasible. Keep the file systems the
> same size, so that relocation will be easy if it is necessary.

I'm not sure I'm following you here. What's the advantage of breaking up RAID sets into multiple file systems? Corey, Abbey, & Dechichio explicitly admonish against this idea in "Tuning Oracle." p. 8.

Now, having multiple data files per tablespace, even on the same file system, has worked very well for me in the past. I can then easily move them around to different file systems as needed.

> Also, use
> symbolic links to address the files, and use the links in the tablespace
> definition.

I've tried this. Works great. Highly recommended.

> Make your stripe width a multiple of the Oracle blocksize,
> i.e. stripe size = db_block_size * db_file_multiblock_read_count. ex. 8k
> block, 16 block multiread = 128k stripe.
 

>
> You might want to go to www.oracle.com to check for a white paper on this
> topic. Think I saw one there.

I've looked and can't find anything there. Maybe I just missed it.

> Also, check old IOUW conference
> proceedings. There were some good presentations on this by Cary Millsap
> around 2 years ago.
>
> Good luck!
>
> --
> ================================================
> Gregory A. Burris
> Practice Manager, Performance and Architecture Group
> Oracle Consulting Services
> Troy, MI
> Office: 810-614-5029
> Pager: 800-467-3700 pin 6026949

Joseph

---

Joseph Thvedt
jthvedt_at_brookings.net

"A noble spirit embiggens the smallest man." Jebediah Springfield a.k.a. Hans Sprungfeld

O- Received on Thu Feb 06 1997 - 00:00:00 CST