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    SubjectRe: Journal FS Comparison on IOzone (was Netbench)

    Andrew Theurer wrote:
    > On Monday 27 August 2001 01:24 pm, Randy.Dunlap wrote:
    > > Hi,
    > >
    > > I am doing some similar FS comparisons, but using IOzone
    > > ( instead of Netbench.
    > >
    > > Some preliminary (mostly raw) data are available at:
    > >
    > > (updated today).
    > >
    > > I am using a Linux 2.4.7 on a 4-way VA Linux system.
    > > It has 4 GB of RAM, but I have limited it to 256 MB in
    > > accordance with IOzone run rules.
    > >
    > > However, I suspect that this causes IOzone to measure disk
    > > subsystem or PCI bus performance more than it does FS performance.
    > > Any comments on this?
    > Randy,
    > You are definitly exceeding what the kernel will cache and writing to disk on
    > some tests. I guess it depends on what is more important to you. I think
    > both are valid things to test, and you may want to try not limiting memory to
    > get just FS performace in memory for large files. However, writing to disk
    > is important, especially for things like bounce-buffer. Did you have himem
    > support in your kernel? If so, did you have a bounce-buffer elimination
    > patch as well?


    Sorry about the delay in responding.

    I'm interested in filesystem performance. I'm not trying to
    document IDE vs. SCSI vs. FC performance/price tradeoffs, benefits,

    > Does the storage system/controller have a disk cache? What size?

    Good questions, but I'm having trouble finding answers for them.
    (hence the delay in responding)

    The FC host controller is a QLogic 2200. It is attached to an
    IBM FAStT controller/drive array -- one controller with 10
    attached drives. I've been looking at the IBM FAStT OS console
    interface, but I can't see much cache info there.
    There is one item: cache/processor sizes: 88/40 MB

    > Also, does IOzone default to num procs=num cpus? I didn't see any options in
    > your cmdline for num_procs.

    No, IOzone doesn't default to num_processes = num_cpus.
    That's a command-line option that I didn't use, although I expect
    to do some testing with that option also.

    Thanks for your comments.

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