Date: Thu, 7 Jun 2007 12:34:03 +0200 From: Nico -telmich- Schottelius <nico-freebsd-scsi@schottelius.org> To: Bernard Buri <berni@ask-us.at> Cc: freebsd-scsi@freebsd.org Subject: Re: Recommened U320 SCSI controller (pci-x)? Message-ID: <20070607103403.GA26318@schottelius.org> In-Reply-To: <4667CCA6.3030508@ask-us.at> References: <20070606143430.GA31380@schottelius.org> <466717E5.2070909@ask-us.at> <20070607083147.GA25624@schottelius.org> <4667CCA6.3030508@ask-us.at>
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--y0ulUmNC+osPPQO6 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Bernard Buri [Thu, Jun 07, 2007 at 11:15:18AM +0200]: > We have a "Feiertag=3D=3Dno one is in office" today, Ah, yes, Fronleichnam. > and there was a=20 > technical problem yesterday evening. Some servers are down obviously so= =20 > I cannot lookup which product is built in exactly. I can find out=20 > 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: >=20 > Did you analyze the disk i/o any further ? > My experience with FreeBSD shows, that upgrading the main memory=20 > generously (2 or 4 GB) will allow the system to fill the buffer cache=20 > with file data, while leaving the "Namei lookup cache" constrained to=20 > 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=20 > situation: I run du -h -d1 /usr/ports to fill the Namei cache. Now I=20 > 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. >=20 > Most of the mailserver softwares are using many small files, and I guess= =20 > that the lookup cache should improve the overall performance more than a= =20 > fast drive. If you see low Namei hit rates, perhaps there is information= =20 > available on how to tune the cache ? Will remember that for further systems, but this one almost always has cache-hit rate >=3D 90%. Nico --=20 Think about Free and Open Source Software (FOSS). http://nico.schottelius.org/documentations/foss/the-term-foss/ PGP: BFE4 C736 ABE5 406F 8F42 F7CF B8BE F92A 9885 188C --y0ulUmNC+osPPQO6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFGZ98buL75KpiFGIwRAjEpAJ9ZITDNTbdjbkGX/TzltAGX1YzGbACfVmQY HMUIJj5BKxY2MOv6XtBVhW0= =f0bG -----END PGP SIGNATURE----- --y0ulUmNC+osPPQO6--
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