>It likes a LOT of real memory and it appears that the running instance
consumes the full amount of real memory allocated to it for the duration,
making it unavailable to zOS for paging or any other use.

 

Well, sure-that memory use is Linux caching files in memory. This has all
been explored, analyzed, and solved under z/VM years ago; alas, z/OS doesn't
have the same kinds of controls, so it's going to be a problem with zCX
until and unless IBM adds some knobs.

 

I'm with Dave Jones re "Where's the real value?" I remember when IBM first
proposed what became zCX, I asked what the point was. The answer I got was
"It's politically hard/impossible to get an LPAR created to run z/VM (not to
mention paying for z/VM) or to run Linux on the bare iron". A technical
solution to a political problem is painful to contemplate, but is sometimes
necessary, and it appears that's what zCX is.

 

Running an entire operating system under z/OS that isn't acclimated to doing
so is inherently problematic. Things like Db2 and CICS have spent many, many
years being made into good z/OS citizens (OK, since CICS has always been
under z/OS and predecessors, that's obvious-but Db2 started as SQL/DS on
VM). Sure, IBM can make Linux behave under z/OS, but it's gonna take a
while! And the real value is still unclear to me, beyond the political
hurdles. You're sure not going to run hundreds of zCX containers under z/OS,
I don't think, as you can Linuxen under z/VM.

 

TonyH: My information is that z/OS (MVS) only uses SIE for zCX, so I think
that's just two levels of SIE, which presumably/hopefully means vSIE, which
isn't that bad?

 

...phsiii (who spent four years doing Linux provisioning under z/VM at
Linuxcare and then a few years doing performance of Linux under z/VM, so
feels he has some qualifications to make the above assertions)


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