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RE: New Power8 Disk Perf Issues



fixed


"Steinmetz, Paul" <PSteinmetz@xxxxxxxxxx> wrote on Tue, 26 Aug
2014 18:09:00 GMT:

Sue,

<I will agree for POWER7 and earlier systems. I will disagree
for the POWER8 S814 and S824 models with high function
backplane. The on-board disk IOAs are better than the feature
ESA3 and 5913 adapters used by many on POWER7 for write
intensive and write response time sensitive workloads.>

When you state high function backplane, you're referring to
<Third is high function backplace with 7.6GB of write cache
and maximum drive bays.> correct?


Correct.

So, if using CEC's DASD, you should almost always consider
option 3 from a performance point of view.


Performance answers are always it depends on the workload
requirements.

Also, are you stating the option 3 is equal or outperforms a
5913. So a fully loaded CEC with 8 775gb SSD (5.4 tb useable
with Raid 5) with option 3, high function backplane would be
about the best performance for an i5/0S LPAR.


No, the architecture of a POWER8 is vastly different than its
predecessors. A S824 system unit can have up to 18 SFF3 disk
bays (2.5" HDDs or SSDs) plus up to 8 1.8" SSDs for a total of
26 devices mounted in the CEC.

This compares to 8 SFF disk bays on POWER7 720 and 740 systems
or 6 SFF disk bays on POWER7 770 and 780 systems.







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