Re: disk i/o balancing

Joseph Thvedt <jthvedt_at_brookings.net> wrote in article <32FA53B9.7E9C_at_brookings.net>...
> Thanks. I have a couple of questions & comments:
>
> > 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.
>

There are several reasons.

1. You must still consider partitioning tables into tablespaces by application, to facilitate the ability to segment backups and other administration requiring offline tablespaces. If you can take the entire database offline during these operations, then no biggie.
2. Unless you are using Raid 5, software generated block corruptions can still be replicated across the mirror. If you take a hit on the tablespace header block(s) (a slight possibility to be sure, but there nonetheless), then you disable a great deal of data, potentially for a long period of time.
3. Experience had lead me not to take the "trust me" approach of leaving it up to the OS to minimize my possibilities of I/O contention. Most of the time, it will be OK, but as soon as it's set up that way, something comes along to indicate that more granularity would have been better.

Keep looking for those white papers. If I get a chance to get onto the website, I will see if I can find them and extract them for you. Also, you could contact Support or your sales team. They should be able to point you in the right direction. Finally, email me here or at gburris_at_us.oracle.com if you would like to discuss this in further detail.

Thanks,

-- 
================================================
Gregory A. Burris
Practice Manager, Performance and Architecture Group
Oracle Consulting Services
Troy, MI
Office: 810-614-5029
Pager: 800-467-3700 pin 6026949