using virtual synchrony for CTDB
campt at openmars.com
Fri Oct 6 20:48:19 GMT 2006
> The DMASTER/LMASTER concept is all about resource masters and resource
> affinity. The common case for a file server is not have much contention
> (take for example a server sharing home directories), and lock
> contention is always expensive, no matter what you do.
> What we want to achieve is to not pay the cost of a system engineered
> against locking contention at the expenses of operations where you don't
> have it.
Yup. The point is that you can't scale write workloads within whatever
the locking granularity is by spreading them across more systems. You
_can_ scale read workloads however. So you design your cluster for that.
The CTDB proposal appears to do just that.
Something about the DMASTER redirect is bothering me though. Wouldn't it
be possible to build up 'harmonics' in the cluster since there doesn't
appear to be any terminating condition for redirects? I've seen things
like this happen. Might be better to have a redirect limit of 1 hop or
something like that and then require a return to the LMASTER.
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