Re: Configuring Veritas Quick I/O & Oracle 8

Veritas file system can operate at more or less the same speed as raw (logical) devices. (There is a paper on my website about some testing I have done in this area).

Whilst I have not yet had my hands on Veritas Quick I/O, I am not surprised by the possibility of raw devices apparently performing much more slowly than Unix file systems.

I have frequently come across systems that are protected from bad performance by
file-system buffering - usually because Oracle is being asked to do frequent, fairly large, tablescans which leave Oracle requesting data from the file system, but the file system having it buffered and responding very rapidly.

Your raw performance is probably down to exactly this problem, and if Veritas Quick I/O works by bypassing its file system buffer then it may be that Veritas is suffering from exactly the same problem.

Have a look at your system statistics to see how much of your data acquisition is being done by table scans.

--

Jonathan Lewis
Yet another Oracle-related web site: www.jlcomp.demon.co.uk

Herbert Zarb wrote in message <373d17b6.0_at_news.waldonet.net.mt>...
>Hi,
>
>We are currently performing a number of tests to evaluate the viability of
>using Veritas Quick I/O instead of raw devices for our Oracle databases.
Our
>system is an SUN Enterprise 4500, with Solaris 2.6 and Oracle 8.0.5. We
>tried a long DSS process several times. Whilst using normal UNIX UFS
>filesystems for the data files, this process took around 13 hours to
>complete. However, when we retried the test using Veritas file systems and
>Quick I/O, it is taking MUCH longer - as a matter of fact it's been going
>on for the last 28 hours and it has not completed yet. Also, we had tried
>the run using raw devices and this took around 40 hours to complete -
>initially we discarded this result but now it is starting to look less
>unrealistic.
>
>From the UNIX side of it, there does not seem to be any particular
re-tuning
>to be done when using Veritas file systems & Quick I/O (neither when using
>raw devices if we come to that). Hence I am suspecting that it is either
the
>type of test being done which is accentuating the benefits of normal file
>systems over direct I/O to files, or that there is some Oracle tuneables
>that have not been properly set.
>I would really appreciate any help or advice regarding the matter.
Received on Sat May 15 1999 - 10:23:26 CDT