Recommened U320 SCSI controller (pci-x)?

[Nico -telmich- Schottelius]

Bernard Buri [Thu, Jun 07, 2007 at 11:15:18AM +0200]:
> We have a "Feiertag==no one is in office" today,

Ah, yes, Fronleichnam.

> and there was a 
> technical problem yesterday evening. Some servers are down obviously so 
> I cannot lookup which product is built in exactly. I can find out 
> tomorrow though.

Ok, would be nice to know.

> Are you looking for hardware raid, or do you want to do software raid ?

I think I am now more on the software raid road, if possible, because
the cpus are strong enough and one can change the vendor / bus /
harddisks without problems using sw-raid.

> Another question that comes to my mind:
> 
> Did you analyze the disk i/o any further ?
> My experience with FreeBSD shows, that upgrading the main memory 
> generously (2 or 4 GB) will allow the system to fill the buffer cache 
> with file data, while leaving the "Namei lookup cache" constrained to 
> some degree.

Both sc1425 running here have 2GiB memory, guess that should be enough.

> If you run systat -vmstat 1, you can see everything on one place:

Yep, that's a very nice diag, was notified about that tool some days ago.

> 1.) On the bottom, you can see the actual disk utilization.
> 2.) Above, you can watch the "Namei" cache behaviour.

If I see it correctly, a 99% cache hit should be very good, because
mostly everything comes from the cache?

> 3.) On top, you see Free Memory, that is: memory that is not used at all

About 150 to 100MiB are free all the time.

> So, on my Mac mini which has a very slow disk I face the following 
> situation: I run du -h -d1 /usr/ports to fill the Namei cache. Now I 
> watch the statistics in systat and run du again:
> 1.) I see actual disk i/o happening on my drive
> 2.) I see Namei cache hits dropping to ~45%
> 3.) I see about 300MB of memory unused.
> 
> Most of the mailserver softwares are using many small files, and I guess 
> that the lookup cache should improve the overall performance more than a 
> fast drive. If you see low Namei hit rates, perhaps there is information 
> available on how to tune the cache ?

Will remember that for further systems, but this one almost always
has cache-hit rate >= 90%.

Nico

-- 
Think about Free and Open Source Software (FOSS).
http://nico.schottelius.org/documentations/foss/the-term-foss/

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