Re: Hardware and Performance - OnLine 7.20
In article <358559F8.3F06@bloomberg.net>, kagel@bloomberg.net (Art S.
Kagel) wrote:
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> From: "Art S. Kagel" <kagel@bloomberg.net>
> Newsgroups: comp.databases.informix
> Subject: Re: Hardware and Performance - OnLine 7.20
> Date: Mon, 15 Jun 1998 13:29:28 -0400
> Organization: Bloomberg LP
> Lines: 17
> Message-ID: <358559F8.3F06@bloomberg.net>
> References: <35847C47.65DCECC1@arrakis.es>
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> To: MARTIN <ramp@arrakis.es>
> Xref: news.cix.co.uk comp.databases.informix:66260
>
> MARTIN wrote:
> >
> > I have a question , what improve more the performance RAM or CPU in a
> > systems with uptime from 3 to 6 and with freemen (sar -r) less than 10
> 00
> > .It's a system with 256 MB and one cpu
>
> In your case it may not be an either or situation. You have so little
> free RAM that you will not be able to take proper advantage of a second
> CPU and would probably see little improvement. So in this light the
> priority would have to go to RAM if resources are tight. Of course,
> having added another 64 or 128MB of RAM (and an appropriate amount of
> additional swap disk) you can now make very good use of that second
> CPU. Depending on architecture most systems see an 80%->95% increase
> in system throughput from a second CPU and IDS may improve individual
> queries by even more by parallelizing I/O and processing.
>
> Art S. Kagel
>
In Solaris at any rate, sar -r showing little free memory is not an
indicator of memory shortage. sar -g showing more than a little paging can
indicate memory shortage. Runnable processes ever being swapped
out would be a sure sign of memory shortage. Supposing you do have a
memory shortage, it could be overcome either by adding more memory or by
using less, e.g. by reducing BUFFERS. If you do reduce BUFFERS your read
cache rate and write cache rate (shown by onstat -p) may go down, and so
disk I/O go up, but as long as read cache % >= 95% and write cache %
>=85%, this is considered good.
A run queue consistently > 3 is supposed to show a system is CPU bound, so
adding another CPU, or having a faster one instead, would be expected
to help performance.
Brian Wilkins