On 27/04/2018 8:20 PM, Shane G wrote:
On Fri, 27 Apr 2018 12:40:52 +0800, David Crayford <[email protected]> wrote:
On 27/04/2018 1:38 AM, Tom Marchant wrote:
On Thu, 26 Apr 2018 16:14:49 +0100, Styles, Andy (ITS zPlatform Services) wrote:
Can't shutdown and IPL in 315 seconds.. (well, we can't).
No, but you can move the work to another LPAR in the Sysplex before
the IPL, minimizing the application down time.
That can be done on Windows/Linux systems using virtualization
technologies like VMWare and HyperV live migration. Coupled with
fail-over clustering you can build
reasonably robust systems. The monitoring infrastructure is excellent.
Our distributed sysadmin was showing my HyperV and I was very impressed.
It's not as good as
a full parallel sysplex but good enough for a lot of companies WRT SLAs.
On the way home from Boston Share, I dropped in to VMWorld in Frisco.
One of the sessions was a live migration of an active representative workload
from mainland USA to India. In front of a live audience, with monitors running.
Bloody impressive. And this was Aug/Sept 2013. Even z/VM couldn't handle things
like that, let alone a 'plex.
Just ask google/facebook/amazon what can be done on non-proprietary commodity
hardware to keep systems up and running.
Indeed. The big weakness of distributed systems is the network and the
misguided assumption that the network is stable. Modern databases and
middleware like MongoDB, Cassandra, Kafka etc
have been proven to fail spectacularly when network partitions occur.
And they happen more often then vendors would like to admit with
disastrous consequences. There's an interesting series
of analysis that threw the cat amoungst the pigeons a while back [1].
Mainframe systems don't seem to suffer from the same problems in tightly
coupled sysplexes.
[1] https://jepsen.io/analyses
Shane ...
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