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Re: [Linux-cluster] Interfacing csnap to cluster stack



On Thursday 07 October 2004 02:07, David Teigland wrote:
> - SM is almost exclusively designed for symmetric clustering
> subsystems and almost exclusively for in-kernel use.

Hi Dave, 

The executive summary of your post is "my pristine, perfect service 
manager is for symmetric systems only and keep yer steenking 
client-server mitts away from it."

You may well be right that it is not suited to the task at hand.  My 
interest was more in its notion of layered services than its 
membership-oriented control methods and events (by the way, the 
stop-start-finish terminology is still horribly broken, I thought you 
were going to fix that).

> the server is by definition a single point of failure (something
> absent from symmetric systems.) 

No.  The csnap server is not a single point of failure any more than a 
DLM lock master is.  So either it is not a single point of failure, or 
single points of failure are not absent from your gdlm, choose your 
poison. 

> A prime example is NFS.  RM is able to monitor an NFS server and start
> it on  another machine if it fails.  NFS is probably the model you
> should follow if your system is asymmetric and you want to use RM.

NFS is an awful model.  It keeps almost all its state on the clients, 
and it tries to inhale the entire recovery model into itself, with no 
help from infrastructure.

In contrast, a csnap server keeps almost all its state persistently on 
shared storage, and it is supposed to have a cluster infrastructure 
around to help it do some global processing that is not appropriate for 
it to undertake itself.  You seem to be arguing passionately that yours 
is not the infrastructure we are looking for.  Fair enough, I'd hoped 
for more.

Regards,

Daniel


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