Messages in this thread | | | Date | Sun, 03 Apr 2005 17:38:01 +1000 | From | Nick Piggin <> | Subject | Re: Industry db benchmark result on recent 2.6 kernels |
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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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