Messages in this thread | | | Date | Sun, 29 Dec 2002 20:53:28 -0300 | From | Werner Almesberger <> | Subject | Re: holy grail |
| |
Anomalous Force wrote: > you miss my point. im not saying to model it after tcp/ip. that > was just a reference to a method of data exchange wherein the > data has metadata to describe it.
I understood that. What I was saying is that metadata in a TCP connection is usually not sufficient for restoring the endpoint state.
> it makes full sense in an enterprise with 3000+ users that operates > 24/7/365. no scheduled down-time for kernel upgrades.
I don't disagree with the usefulness of such functionality, but I disagree with the level at which you suggest to implement this.
The approach of trying to migrate low-level kernel state has the following problems/disadvantages:
- complexity - does not allow recovery from corrupt kernel state, as Pavel has suggested - does not support recovery from corrupt hardware state - does not support substitution of infrastructure (e.g. what if I want to fail over to a different machine, maybe quickly replace some non-hotpluggable hardware (*), or even swap that old disk with a new one that has completely different characteristics ?)
So, compared to an approach that implements this at the kernel to user space API level, you get a lot of extra complexity, but miss several very desirable features.
(*) While the "big iron" in your data center may have hot-swappable CPUs and everything, it would be nice if such things could also be done with commodity hardware that doesn't provide such luxury.
> this is not true. if the system were an integral part of the overall > design, then programming would include it apriori.
Making something part of the design alone doesn't guarantee that this is a good approach, nor that it will actually work :-)
> there is a fine distinction between kernel migration, and hot-swap. > in a hot-swap setup, there will be signals pending from devices [...]
Err, yes, but what does your "hot-swap" do that kernel migration doesn't ?
- Werner
-- _________________________________________________________________________ / Werner Almesberger, Buenos Aires, Argentina wa@almesberger.net / /_http://www.almesberger.net/____________________________________________/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |