A failover system does not solve the scalability issue.. which means that you have a full server sitting there doing nothing most of the time when if the load were being balanced across the servers in a "cluster" senario you would also have the scalability..Andrew Kohlsmith wrote:
I would set the "Enterprise Class" bar at five 9's reliability
(about 5.25 minutes per year of down time) the same
as a Class 4/5 phone switch. This would require redundant
design considerations in both hardware and software.
To turn around, let's discuss what we need to focus on to get Asterisk there:
Here's a few bullet points, there's certainly a lot more * Linux platform stability - how? ** Special demands when using Zaptel cards * Redundancy architecture * Development/stable release scheme
Then we have some channel demands, like * Better support for SRV records in the SIP channel
More?
Better sip phone support for primary/secondary proxy (and failover) (note: some phones don't support a second proxy at all; some say they do, but fail at it.)
Maybe some sort of HSRP (hot spare standby protocol, or whatever)
Some form of dynamic config sharing between pri/sec systems
Won't mention external pstn line failover as that's sort of a separate topic, or loss of calls in flight, etc.
I'd guess part of the five-9's discussion centers around how automated
must one be to be able to actually get close? If one assumes the loss
of a SIMM the answer/effort certainly is different then assuming the loss of a single interface card (when multiples exist), etc.
I would doubt that anyone reading this list actually have a justifiable
business requirement for five-9's given the expontential cost/effort
involved to get there. But, setting some sort of reasonable goal
that would focus towards failover within xx number of seconds (and
maybe some other conditions) seems very practical.
Also a failover system would typically only be 2 servers, if there were a cluster system there could be 10 servers in which case five 9's should be easy..
Later..
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