openstack team mailing list archive

[Ryan Lane <rlane@xxxxxxxxxxxxx>]

> I know. That's what makes them a poor fit for "the cloud".
>

Meh. Private clouds will still use applications like this. I think
"the cloud" is great for cloud providers, but why limit nova's
usefulness to just cloud providers?

"The cloud" way of doing things pushes the responsibility of keeping
applications alive to the client. There's a lot of clients that don't
have this level of sophistication.

>> Hardware HA is useful for more than just poorly designed applications
>> though. I have a cloud instance that runs my personal website. I don't
>> want to pay for two (or more, realistically) instances just to ensure
>> that if my host dies that my site will continue to run. My provider
>> should automatically detect the hardware failure and re-launch my
>> instance on another piece of hardware; it should also notify me that
>> it happened, but that's a different story ;).
>
> I'm not sure I count that as High Availability. It's more like
> Eventual Availability. :)
>

So, this is one HA mode for VMware. There is also a newer HA mode that
is much more expensive (from the resources perspective) that keeps a
shadow copy of a virtual machine on another piece of hardware, and if
the primary instance's hardware dies, it automatically switches over
to the shadow copy.

Both modes are really useful. There's a huge level of automation
needed for doing things "the cloud way" that is completely
unnecessary. I don't want to have to monitor my instances to see if
one died due to a hardware failure, then start new ones, then pool
them, then depool the dead ones. I want my provider to handle hardware
deaths for me. If I have 200 web servers instances, and 40 of them die
because they are on nodes that die, I want them to restart somewhere
else. It removes all the bullshit automation I'd need to do otherwise.

- Ryan Lane