Hi,
There are some services in sipXecs, which are SPOF even in redundant
sipXecs deployments. These are: the mediaservices(ACD, conferencing, VM)
and the config(admin and user portal).
Our goal is to build a fully HA system. We have come up with multiple
ideas and some of them we discussed briefly with the sipx developers
already. The most promising idea we have to date looks like this:
.------------------------.
.---------------------------------------------.
| Site 1 | | Site 2
|
| | |
|
| .--------------------. | | .-------------------.
.-------------------. |
| | Node 1 | | | | Node 2 | | Node 3(cs)
| |
| | (service IP) | | | | | |
| |
| | | | | | | |
| |
| | .---------------. | | | | .---------------. | | .---------------.
| |
| | | Proxy(pri.) |----------->| Proxy(sec.) | | | | Proxy(pri.) |
| |
| | '---------------' | | | | '---------------' | | '---------------'
| |
| | .---------------. | | | | | | .---------------.
| |
| | | Config | | | | | | | | Config |
| |
| | '---------------' | | | | | | '---------------'
| |
| | .---------------. | | | | | | .---------------.
| |
| | | Mediaservices | | | | | | | | Mediaservices |
| |
| | '---------------' | | | | | | '---------------'
| |
| | | | | | | |
| |
| '--------------------' | | '-------------------'
'-------------------' |
| | | | |
|
'-----------|------------'
'---------------------------------|-----------'
| .------------------------. |
| | Replicated config | |
'----------->| (using DRBD) |<-----------'
'------------------------'
Figure 1: Before failover
The idea behind is to extend the basic redundant configuration
sipfoundry suggests(Node 1 on Site 1 and Node 2 on Site 2) with a 3rd
node(Node 3) on Site 2. The Node 3 acts as a cold standby primary node
and has all configuration files synced to/from the primary server.
The configuration directories(/etc/sipxpbx and the /var/sipxdata)
between the primary Node 1 and the cold standby Node 3 would be
replicated using DRBD, which is a filesystem replication facility
available in CentOS.
Since the configuration is shared, the Node 1 and Node 3 has to have
same IP address as we don't want to mess around with the config files.
To avoid IP conflicts, there would be 3 IP addresses for the Node 1 and
Node 2. From the three, one would be the "service IP", for which sipXecs
is configured. When both primary nodes start, they come up with one of
the non-service IP address and with some mechanism they decide who
should be active. The active one takes over the service IP(using
ifconfig eth0 for eg) and starts the sipxecs services. When failover
happens(previous active goes down), the other node takes over the
service IP and starts sipXecs service.
.------------------------.
.---------------------------------------------.
| Site 1 | | Site 2
|
| (DOWN) | |
|
| .--------------------. | | .-------------------.
.-------------------. |
| | Node 1 | | | | Node 2 | | Node 3
| |
| | (DOWN) | | | | | | (service IP)
| |
| | | | | | | |
| |
| | .---------------. | | | | .---------------. | | .---------------.
| |
| | | Proxy(pri.) | | | | | | Proxy(sec.) |<----| Proxy(pri.) |
| |
| | '---------------' | | | | '---------------' | | '---------------'
| |
| | .---------------. | | | | | | .---------------.
| |
| | | Config | | | | | | | | Config |
| |
| | '---------------' | | | | | | '---------------'
| |
| | .---------------. | | | | | | .---------------.
| |
| | | Mediaservices | | | | | | | | Mediaservices |
| |
| | '---------------' | | | | | | '---------------'
| |
| | | | | | | |
| |
| '--------------------' | | '-------------------'
'-------------------' |
| | | | |
|
'-----------|------------'
'---------------------------------|-----------'
| .------------------------. |
| | Replicated config | |
'----------->| (using DRBD) |<-----------'
'------------------------'
Figure 2: After failover
Since it's probably not only us who'd like to have a fully redundant
sipXecs we decided not to do it undercover, but share our ides/progress
with the community. I hope we can come up with something usable.
Looking forward for your comments,
Chris
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