Re: Raw Logical Volumes vs. Unix File Systems

In article <Cuozwt.76p_at_idm.com>, tmb_at_idm.com (Thomas M Buccelli) writes:

Lynn Osburn (losburn_at_teal.csn.org) wrote:
> In article <CunMG5.53u_at_shellgate.shell.com>,
> Stephen Pace <pace_at_shell.com> wrote:
> >I need some information about creating Oracle databases on Raw Logical
> >Volumes vs. standard Unix file systems.
> >What are the advantages? Are they that much faster? We have a 6-8 GB
> >Oracle 7 database sitting on an RS/6000 590, and we are starting to see
 

> The Book (Oracle7 Administrator's reference guid) says a performance
> improvement of 10-15% is a reasonable expectation, since you are not
> going thru the AIX kernel buffers and the filesystem on the way to the
> disk. When we were installing on my most recent HP, the guy from
> Oracle Core Technologies, indicated his experience was more like 5-7%.
 

> I had 130 installations of Oracle on AIX (3.2.2) and we elected to go
> with regular filesystems because:
> - backup and restore was much more robust and flexible
> - using LVM, we could tune the placement of the datafiles on the disks,
> as well as actual placement on the individual disks (center vs. edge)
> - we had the option of striping and mirroring at the LVM level as a
> performance option when we grew the DB large enough or management
> decided the system was critical enough for mirroring.
> - performance differential not large enough to compensate for extra
> hassle.
 

>We use Oracle on RAW LVM's that are stripped and mirrored and have had
>no problems whatsoever. For backup we simply split off a mirrored copy
>of the raw device and back them up with Omniback Turbo (a very nice,
>although slightly expensive product).
 

>Tom

This information is getting a little old since it is based on benchmarks we were doing 2 years ago on various hardware but we found that Oracle on AIX was slightly faster with Unix files instead of raw. After we discovered this we were told by Oracle that they recommend using the Unix files on several platforms including AIX because it was either the same or even faster than raw and certainly easier than raw for backup and recovery. Our benchmark was a mix of simultaneous queries on a large (12G) decision support database.

On AIX I'd use LVM and Unix files for the convenience.

Scott Cary
Database Administration
BCBSO Received on Thu Aug 18 1994 - 07:30:03 CEST