On 29.11.2012 10:09, Patrick Spinler wrote:
Several of the things I've seen mention of as specific Z advantages
in
this thread, though, are just as easily doable on other platforms.
For instance someone mentioned fast cloning on Z; however I know a
guy
here who has a virtualbox on top of Solaris/x86 using ZFS where he
does
about 30 seconds to clone a windows virtual desktop. Someone else
mentioned live adding memory and connecting disconnecting disk.
That's
been possible on vmware esx for quite some while.
Yeah, I would amplify that caution. Showing up to a group of people
who've worked with ESX or RHEV (for example), and telling them that one
of the advantages of zVM is thin provisioning from a templated image
will have them likely discard anything one says thereafter.
Be careful about touting something as a Z specific advantage when it
might not be all that specific.
Or benefits that are more annoying to implement - sharing pages between
guests is a great feature, but it's painfully manual in zVM compared
with (say) KVM/RHEV.
From my perspective some the pros would be:
* Managing zVM programmatically is a first-class experience. Many
virtual environments are managed through a GUI, which is easy, but
bulk-changes require using an API which doesn't always seem to have been
designed with a great deal of care and attention.
* Ability to sustain high utilisation: we have Oracle DBs on zLinux
which can run their LPAR at 100% for hours at a time without creating
problems for the applications which depend on them. This is not the
norm in Intel virtual environments; I will add the caveat that it's not
universal to all workloads (WebSphere apps tend to behave very poorly in
the same conditions).
* Required CPU count sometimes decreases: depends on the nature of the
application, but, for example, we've crammed an 8-core Lintel Oracle DB
into a 5 CPU Z10 footprint (which other DBs co-located). While the cost
of the Z hardware and software stack is pretty eyewatering, being able
to reduce the app software license can balance that out in some
circumstances.
* Advantageous licensing for some product stacks. We have some key
software stacks which are substantially cheaper to license top-to-bottom
on Z than on Intel, cheap enough that the hardware/zVM cost is
inconsequential.
* Ability to get excellent overcommit: depends on the application to an
extent (we find Java apps don't overcommit very well compared to
compiled ones, for example), but in a happy days scenario we can get
acceptable performance with heavily overcommited CPU. Memory is harder
with Java and Oracle, because paging the heap or the SGA respectively
makes for very unhappy campers.
--
Rodger Donaldson
[email protected]
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