John wrote regarding 'Re: [SLE] Mail Server purchasing decision' on Sat, Sep 04 at 00:59:
On Friday 03 September 2004 07:26 am, Danny Sauer wrote:
They used the 3ware controller in both tests, using the 3ware controller's on-board cache in both cases. What kind of person is gonna buy a RAID controller and then run each disk on the controller individually, using software RAID instead of the hardware raid that they paid for? I
ME for one.
Look, the performance is BETTER!
I'll grant that - under a synthetic benchmark the performance gain is marginal. Whoopie. Software RAID finally catches up to be "as good as" hardware RAID, and maybe even a little better under circumstances unlikely to be encountered in regular use. Where's the benchmark under load, like anyone who can justify RAID will be experiencing? Nowhere? Hmm... Also note that they only used XFS on the hardware raid setup - the test was mostly to compare *filesystem* performance. Compare HWXFS to SWXFS, and note that the hardware solution is faster in some of the cases.
And CPU utilization for software raid is a MYTH, left over from the 486 days.
To quote the other reply: "got numbers?" There are some numbers on that test page linked to - they show the hardware RAID setup using about 1/3 of the CPU of the software RAID pretty consistently. Ok, so the CPU's only used a little now. It's still greater than with a hardware RAID controller. Windows XP uses more resources than '95 did, and programs are getting bigger all the time. What the heck? We've got memory and processor to spare now! The CPU is *still* used more, with no regard for whether or not the cycles consumed are important to the application at hand. I use dedicated hardware for sound, network interfacing, video, and disk controlling. All of that could be done in the processor, and the cycles consumed wouldn't really hurt anything. Are you running a winmodem now, since the processor can do some DSP on the phone signal "as well as" a hardware modem? Running sound and network over USB since it's "almost as good as" hardware on the PCI bus? Using integrated video without any 3D acceleration for those games, since the processor "can" do it? I dunno. Maybe it's the part of me that builds engines and prefers to eliminate things like an engine-driven fan, because it limits the amount of power I can use at full throttle. I don't drive at full throttle all the time, but I want as much engine as possible to make me go forward when I put the hammer down. Software RAID is that engine-driven fan that cools better under some situations, but is worse in other situations and is taking a possibly imperceptable amount of full-load speed away from me. Feel free to have the fastest benchmark computer around. I've got more cycles available when I *use* my computer.
Read the Article.
I did. Twice now. --Danny