Inside System Storage -- by Tony Pearson

Tony Pearson Tony Pearson is a Master Inventor and Senior IT Specialist for the IBM System Storage product line at the IBM Executive Briefing Center in Tucson Arizona, and featured contributor to IBM's developerWorks. In 2011, Tony celebrated his 25th year anniversary with IBM Storage on the same day as the IBM's Centennial. He is author of the Inside System Storage series of books. This blog is for the open exchange of ideas relating to storage and storage networking hardware, software and services. You can also follow him on Twitter @az990tony.
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Tony, a great post, and I have long since given up posting comments on Hu's blog as they always get censored out (if they question anything he says) <div>&nbsp;</div> One thing that should also be noted, is that anything doing 100,000 iops at 200us response time is either cache hit (most likely) or running from SSD. <div>&nbsp;</div> I suspect this measurement is carefully done, HDS have an "on-chip" cache in their host interfrace protocol chips - its quite small, but if you "re-read" the same blocks over an over, then it doesn't even leave the host protocol chip, just gets serviced from there. Probably the reason for only have 1 volume, and probably a very small one at that, that keeps being re-read! <div>&nbsp;</div> In all things performance, clarity, full disclosure and comparing apples to apples to key. Thats one of the reasons I like the SPC benchmarks, its the same test for everyone - obviously the number of drives and how its configured can change, but full disclosure is provided by the reports available on the SPC website. <div>&nbsp;</div> Hopefully everyone understands that performance graphs like that one are not worth (i would say the paper they are printed on) but maybe that should be the energy used to display them on your screen ;) <div>&nbsp;</div> Barry

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