gco

[tanislavm]

hi,

i understand that a gco is a virtual(global) cluster formed from 2 vcs clusters each one in a separate site.the heartbeat between nodes from the sites goes over the wan?the gab traffic that updates all the nodes between the 2 sites,goes over this wan between sites?

[Gaurav_S · Accepted solution]

Hi,

Yes, the heartbeat between two sites goes via ICMP traffic over WAN. GCO uses resource called WAC to form this heartbeat.

If you look at GAB output, GAB will not form a membership with remote site, GAB will have local membership with local nodes. You can identify remote nodes using "hastatus -sum" command which will show status of remote site

You can query status of heartbeat using "hahb" command ..

https://sort.symantec.com/public/documents/vcs/6.0/solaris/productguides/html/vcs_admin/ch18s02s06.htm

G

[Gaurav_S]

These posts may help you to gain further understanding ..

https://www-secure.symantec.com/connect/forums/vcs-global-cluster-configuration

https://www-secure.symantec.com/connect/forums/gco-configuration-between-2-nodes-cluster-and-1node-cluster

G

[Sunil_Yadav · Accepted solution]

Hi,

Your understanding on GCO is right. Global Cluster Option(popularly known as GCO) is a global cluster formed from atleast 2 VCS clusters, each one in a separate site. This clusters are NOT geographically co-located(usually, separated by more than 80 kilometers).

HB between clusters: There is ICMP based heartbeat between clusters, which goes over the WAN. You can check remote clusters HB connectivity using “hahb” command.

E.g. In 2 cluster GCO(Pune and Mumbai), “hahb –state” executed from Pune gives connectivity between it and Mumbai cluster. 

# haclus -state
#Cluster     Attribute                Value
Pune         ClusState                RUNNING
Mumbai       ClusState                RUNNING

# hahb -state
#HB          Attribute     Scope      Value
Icmp         State         Mumbai     ALIVE

Message/State exchange between cluster: Wide-Area Connector(WAC) process runs on one of the node in each cluster. It is used for message/state exchange between clusters. This process listens for connection from remote clusters on port number 14155(default wac port). It is configured in ClusterService group.

GAB: GAB maintains membership between local nodes of a cluster. It never spans across clusters. 

Thanks & Regards,
Sunil Y

[mikebounds]

Just to clarify, LLt/GAB is very "chatty" so will communicate all state and config changes down to resource level between nodes in a local cluster.  For GCO, there is no GAB between sites and instead there is a "wac" (wide area connector) resource in the ClusterService group which communicates with the wac resource in the other globally connected clusters (as Sunil says above).  The wac resource is a lot less chatty and only communicates state of group and cluster (not resources).

The wac resource communicates on the address specified by the "ClusterAddress" cluster attribute and you also have a global heartbeat which is normally the same IP, but it can be a different network if you have one and the heartbeat just transmits AYA (are you alive).

Mike