
Processor Utilization Difference Between IBM AIX and Linux on Power - luu
http://www.ibm.com/developerworks/library/l-processor-utilization-difference-aix-lop-trs/index.html
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kpil
All I know is that we once had to temporarily move a cvs repository from a
brand new and crazy expensive pSeries 660 (?) running AIX to a really old and
retired Pentium III laptop that we had found in a drawer and installed linux
on. This was almost 15 years ago, but the laptop was easily 3 years old at
that time - possibly older and positively not a 4 or 6 core server with
gigabytes of ram and a big SCSI raid array.

The linux laptop was then connected to a well used wan-connection in another
location, and we tunneled to it using ssh, instead of just accessing it on the
100 mbit lan, and sent out an apologetic email notifying the developers that
things would be really slow until we had sorted things out with the AIX
systems. ( They had to be moved to another location.)

We found to our surprise that the throughput dramatically improved and
checkout times where reduced to almost nothing compared to the AIX machine it
usually ran on.

Now, maybe CVS is an exceptionally bad workload for AIX or something, but I
doubt that it's an uncommon workload. AIX might possibly scale to more CPUs
efficiently, but it was a clear disappointment nevertheless.

~~~
mattzito
It's entirely possible back in those days that you had a tiny LPAR (VM) for
your CVS data on a big pSeries box that was shared with a bunch of other
resources.

On top of that, it wasn't uncommon to connect those tiny LPARs to shared
storage RAID arrays with hundreds of machines on the same array, and allocate
them a tiny chunk of two or three disks, and deal with all the contention
there.

During that time period, I worked for a hot second at EMC, and was always
fascinated to see these types of configurations - where it was very clear you
could get MUCH better price/performance by buying Linux pizza boxes and
connecting them to local storage - but back in those days it was not
acceptable at big companies to do that.

On the flip side, those pSeries and high-end Sun boxes _screamed_ when they
were optimized for high I/O and high performance workloads. 15 years ago, and
you'd see clusters of these pSeries boxes processing 400k-500k writes/second
and up on Oracle and DB2. Truly impressive stuff for 2000 & 2001.

~~~
kpil
Hm, no not really. The cvs daemon had the whole machine for itself.

~~~
kjs3
Hm, bullshit. Seriously.

~~~
kpil
Seriously not bullshit.

To be fair it can be due to a crappy cvs port or related to something that cvs
do that does not work well on the non-unixy memmory mapped io model on AIX.

~~~
kjs3
I've used AIX since it ran on the RT. I've used CVS since a buddy said
"hey...this guy has some shell scripts that work better than SCCS" (i.e. the
late 80s). I've done OS performance analysis for decades. I'm quite clear on
how those boxes perform. Quit doubling down on the bullshit that an unloaded
660 with server class I/O is outperformed by a mobile P3 cramming data down a
laptop IDE bus. It never happened. What happened is something like what
mattzito described and you just have no idea how real systems are deployed and
managed.

------
dsr_
Once upon a time a customer asked why Linux was more efficient on the same
Power hardware than AIX. IBM assigned a customer engineer to write a paper
explaining this, making sure that IBM's own product looked good no matter
what.

This paper may or may not mean anything else.

~~~
coleca
Back at my last employer when we were looking at setting a new server standard
platform. I once got pulled into an all-day meeting with our IBM rep and a
contingent of IBM sales guys from the Power division and another contingent of
IBM Intel server guys. It was pretty comical listening to their conflicting
sales pitches and the side conversations during the breaks where the IBM Power
guys would bad-mouth the IBM Intel guys and vice versa when the others were
out of the room.

I also had some interesting conversations with some of the Websphere product
team at the IBM lab in Toronto where they told us "off the record" that we'd
get better performance running Websphere Commerce Server on Linux vs AIX
according to their internal tests and that they develop first for Linux and
port to AIX.

I've always liked AIX and found the tools and overall experience very solid.
It's just so darn expensive to scale and maintain it.

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DannyBee
As true or not true as this may be, it's worth pointing out:

The users are highly likely to continue to measure things the wrong way, and
come up with the wrong answers, until you change the way you display numbers.

Regardless of the good or bad reasons[1], telling users to stop reading the
numbers and comparing them never works in practice.

[1]they say: "PURR- and SPURR- based processor utilization were introduced.
This helps better in the CAPEX planning and actual performance expectation in
the SMT8 mode when compared to the single-threaded mode.". I'm not sure i
would ever use these numbers directly for capex planning, but okay .....

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SIGALARM
so.. a Unix operating system that IBM developed specifically for the
rs6000/pseries/power8 servers runs better than Linux. shocking.. even more
shocking that the article is hosted on IBM's own site to tell us so.

obviously, AIX has existed longer than Linux, so it's code maturity is better.
Linux on the other hand runs on way more processors then AIX has ever existed
on. with the flexibility and portability that Linux has to new processors
there is going to be a processor specific performance drop.

~~~
kjs3
So supporting more platforms at the cost of performance is a uncontested good?
Not for everyone, for every use case. AIX has it's place, just like Linux.

