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    SubjectRe: Industry db benchmark result on recent 2.6 kernels
    David Lang wrote:

    > On Sat, 2 Apr 2005, Andreas Dilger wrote:
    >
    >>> given that this would let you get the same storage with about 1200
    >>> fewer
    >>> drives (with corresponding savings in raid controllers, fiberchannel
    >>> controllers and rack frames) it would be interesting to know how
    >>> close it
    >>> would be (for a lot of people the savings, which probably are within
    >>> spitting distance of $1M could be work the decrease in performance)
    >>
    >>
    >> For benchmarks like these, the issue isn't the storage capacity, but
    >> rather the ability to have lots of heads seeking concurrently to
    >> access the many database tables. At one large site I used to work at,
    >> the database ran on hundreds of 1, 2, and 4GB disks long after they
    >> could be replaced by many fewer, larger disks...
    >
    >
    > I can understand this to a point, but it seems to me that after you
    > get beyond some point you stop gaining from this (simply becouse you
    > run out of bandwidth to keep all the heads busy). I would have guessed
    > that this happened somewhere in the hundreds of drives rather then the
    > thousands, so going from 1500x73G to 400x300G (even if this drops you
    > from 15Krpm to 10Krpm) would still saturate the interface bandwidth
    > before the drives
    >

    But in this case probably not - Ken increases IO capacity until the CPUs
    become saturated.
    So there probably isn't a very large margin for error, you might need
    2000 of the slower
    SATA disks to achieve a similar IOPS capacity.



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