Toggleplex, is it a IBM official technique? any shop applied this? We got 8
individual LPARs without sysplex and you knew how pains each time we IPL.
在 2009/9/7上午10:00，Timothy Sipples <[email protected]>寫道：
Cheryl Watson writes:
>And I strongly believe that a parallel sysplex environment
>that leaves the applications available to users 100% of the
>time is the best solution. Once you implement such a
>configuration, it doesn't require you to keep any given
>LPAR up for several months at a time.
To expand on Cheryl's excellent point, there is an advantage to Parallel
Sysplex (including single frame implementations) in terms of software
maintainability. The preventive maintenance policy that Cheryl describes
is
a very reasonable one, but some single production LPAR customers still
find
it difficult to follow because they are understandably reluctant to
schedule a user service interruption. Parallel Sysplex offers distinct
advantages in supporting reasonable preventive maintenance practices,
rolling version and release upgrades, and so on. It provides a very useful
"safety net."
Of course it's still important to test any sort of software changes before
rolling them into production. And, of course, the benefits of Parallel
Sysplex (single frame or otherwise) must be weighed against the
(comparatively modest) costs. I think Parallel Sysplex is presently
under-exploited (on average, in general). But things are changing.
I should also mention that, even short of a Parallel Sysplex, it is
possible for a single frame customer to have at least one cold or warm
standby LPAR in addition to the "live" production LPAR. It depends on the
application architecture(s) how useful this is, but it is always at least
somewhat useful if you cannot get to a Parallel Sysplex implementation
immediately. I'm not sure what to call this approach -- maybe a
"TogglePlex"? Assuming reasonable operations skill you can reduce service
outage windows substantially with a TogglePlex approach. Basically you
apply whatever software updates you want to the standby LPAR, declare a ~2
minute "soft outage" at 2:00 am Sunday morning (or whenever), and, at
that time, point all users over to the updated LPAR. That now becomes the
production LPAR. The next time there's a service update, toggle in the
other direction. With DVIPA, automation, and other dynamic features the
outage can be quite minimal or even imperceptible, depending on the
application and middleware. And, if necessary, you can fall back much
faster, because you keep the backlevel LPAR up and running (at the old
software level) until you're convinced everything is fine with the new
level LPAR. With a TogglePlex you don't force users to wait for applying
maintenance or IPLs. In fact, you can stretch out the IPL within a softcap
if helpful. (There's no rush.) And any IPL problems will not cause user
interruption, because you're not taking any IPLs during the window. So you
can do as many IPL rehearsals as you want, too.
Anybody using a TogglePlex approach today? (And what do you call it? Is
there a better name?) What sort of outage window is the result in your
particular environment?
Apologies if this suggestion is just way too obvious, but perhaps there
are
some newer folks unfamiliar with this (probably old-school) approach.
- - - - -
Timothy Sipples
IBM Consulting Enterprise Software Architect
Based in Tokyo, Serving IBM Japan / Asia-Pacific
E-Mail: [email protected]
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