On 2008-06-19T22:52:55, Xinwei Hu <[EMAIL PROTECTED]> wrote:
> > True. It is possible to break sfex, but the probability that that
> > is going to happen is extremely low and could be due only to a
> > very pathological timing. One way to make this probability still
>
> From my previous experience, I always got _NO_ from customers when
> there are possibility to data corruption.
> So I don't think "extreamely low" is a valid excuse. ;)
But it's always just "extremly low". Even STONITH could fail (the device
could be misconfigured to reset the wrong outlet, or report success when
it in fact failed), there could be issues in the very HA stack, the
kernel could cause data corruption in the fs, the storage could fail,
etc. And that's just random failure, ignoring malicious attackers or
careless sysadmins.
We're never 100% certain.
sfex relies on timing, yes, but with such considerable safety margins
that it's "safe enough". NCS SBD basically trusts the other nodes too.
I think it would be a valuable addition, in particular if it could get
it into daemon mode. This could be the first step towards a real "quorum
resource" which a future quorum plugin framework could utilize, too.
> dskcm has it's own problem too.
> Heartbeat doesn't support the idea of "link priority" or "link
> fallback", so the disk is always up busy for the communication.
> It consumes several hundred KBs of disk I/O bandwidth constantly.
>
> And as we are switching to openais stack, I don't think I'm going to
> improve it any further.
>
> dskcm attracted a lot of interest when people are testing/comparing
> different HA solutions.
> I did several POCs on this myself. But I haven't awared anyone use it
> in _production_ environment yet.
It would be interesting to see whether this could be added to openAIS.
Regards,
Lars
--
Teamlead Kernel, SuSE Labs, Research and Development
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde
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