[Info-vax] Ksplice equivalent for VMS ?

[Dan Cross]

In article <vp5dig$2dnk8$1 at dont-email.me>,
Arne Vajhøj  <arne at vajhoej.dk> wrote:
>On 2/19/2025 2:50 PM, Robert A. Brooks wrote:
>> On 2/19/2025 14:10, Arne Vajhøj wrote:
>>> On 2/19/2025 10:05 AM, Robert A. Brooks wrote:
>>>> On 2/19/2025 08:25, Simon Clubley wrote:
>>>>> Oracle have a kernel patching tool called Ksplice that they acquired
>>>>> back in 2011. It allows their support contract Linux users to apply
>>>>> many Linux kernel patches without having to reboot the server:
>>>>>
>>>>> https://en.wikipedia.org/wiki/Ksplice
>>>>>
>>>>> Given the high-availability mindset for VMS users, I wonder if VSI ever
>>>>> considered creating something similar for VMS ?
>>>>
>>>> No.
>>>
>>> What about process migration?
>> 
>> Like Galaxy on Alpha?
>
>I thought Galaxy was multiple logical systems on one physical system.
>DEC answer to IBM LPAR.
>
>I am thinking about a scenario like:
>* cluster with node A and B
>* critical process P that for whatever reason does not work
>   running concurrent on multiple nodes runs on A
>* node A needs to be taken down for some reason
>* so VMS on node A and B does some magic and migrate P from A to B
>   transparent to users (obviously require a cluster IP address or
>   load balancer)

While this may be an acceptable method to "hotpatch" a host with
minimal disruption to whatever workload it's running, it is
completely unlike what ksplice does.  For one, it requires that
sufficient resources exist in wherever you'd migrate the process
to for the duration of the update.  Moreover, it requires that
all aspects of state that are required to resume execution of
the process are accessable and replicable on other, similar
hardware.

Many hyperscalar cloud providers do something similar for
updates, but there are serious limitations and downsides; for
example, direct passthru to hardware devices (storage, compute
accelerators, etc) can make it impossible to move a VM.

Ksplice updates code in the running system, basically thunking
out function calls to point to new code.  It has fairly
significant limitations, but doesn't require any sort of
migration.

        - Dan C.