On 22 Jan 2016 17:43, "James Bottomley" < [email protected]> wrote: > > On Fri, 2016-01-22 at 14:58 +0100, Premysl Kouril wrote: > > Hi Matt, James, > > > > any thoughts on the below notes? > > To be honest, not really. You've repeated stage two of the Oracle > argument: wheel out benchmarks and attack alleged "complexity".
Sorry fo that, it is true that it is just our conclusion which is not based on any deep analysis. > don't really have a great interest in repeating a historical argument. > Oracle didn't get it either until they released the feature and ran > into the huge management complexity of raw devices in the field, so if > you have the resources to repeat the experiment and see if you get > different results, be my guest. > > The lesson I took from the Oracle affair all those years ago is that > it's far harder to replace well understood and functional file > interfaces with new ones (mainly because of the tooling and historical > understanding that comes with the old ones) than it is to gain > performance in existing interfaces. Ok, point taken. I agree this can be a problem. > > The 3x difference in the benchmarks would seem to indicate a local > tuning or configuration problem, because it's not what most people see. > What the current benchmarks seem to show is about a 1-5% difference > between the directio and the direct to block paths depending on fstype, > how its tuned, ioscheduler and underlying device. I will try to find problem in our configuration and re-run our benchmarks. By chance do you have some more information (and possibly configuration) about the bechmarks you are mentioning? Thanks, Prema
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