Date: Mon, 02 May 2005 19:33:18 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: "Steven Hartland" <killing@multiplay.co.uk> Cc: Robert Watson <rwatson@freebsd.org> Subject: Re: Very low disk performance on 5.x Message-ID: <19122.1115055198@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 02 May 2005 17:43:16 BST." <003901c54f36$0c64ad40$b3db87d4@multiplay.co.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
In message <003901c54f36$0c64ad40$b3db87d4@multiplay.co.uk>, "Steven Hartland" writes: >Ok from what your saying it sounds like RAID on FreeBSD is useless >apart to create large disks. Now to the damaging facts the results >from my two days worth of testing: Now, cool down a moment and lets talk about what you _really_ have measured. You have measured the end to end performance: you include /dev/zero, dd(1), filesystem, disk device driver, hardware and disks. As such that is a fair end-user benchmark, but unfortunately it doesn't really tell us anything useful for the purpose of this discussion. If you are going to do a high-performance setup, you should not just take the "out-of-box" settings, you should optimize for the configurations particular features. Testing end-to-end means that we have very little to go from to find out where things went wrong in any one instance. But anyway: here are some questions which I wonder about ? Does the linux and FreeBSD filesystem offer the same semantics with respect to integrity ? Ie: if one is asyncronous mode the comparison is not a fair comparison. Just because you chose the default in each case doesn't mean you got the same thing. Does any of the drivers change the settings/modes of the controllers use of cache ? (this may be hard to determine without looking at driver sources. In particular, are you sure that the RAID-5 logical device was in the same exact state and location for each run ? Did you remember to disable all the debugging in FreeBSD 6-Current ? (see top of src/UPDATING) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19122.1115055198>