Forum Discussion

cmoreno1978's avatar
cmoreno1978
Level 3
14 years ago

Cluster configuration - RDC or GCO?

Hi all, and thanks again for your help   In other discussions at the forum was asking about the possibilities of setting up a single node cluster with GCO option. As the analysis progressed, we r...
business continuity
Cluster Server
  • Wally_Heim's avatar
    Wally_Heim
    14 years ago

    Hi cmoreno1978,

    It looks like you can deploy an RDC or a GCO configuration if you want.  Althought it is recommended to have multiple heartbeat links when configuring a RDC configuration.

    The main difference that you will need to keep in mind if the way the two of them do failover between the sites.

    A RDC is configured as a single cluster and will fail the service group between the two sites automatically.  With this configuration and default settings, the remote site will always try to bring up the service group if communications are lost to the primary site.  The default settings of the RVGPrimary resource will perform a take over in this case and may cause some issues with data loss if the replication link is not up to date.

    A GCO, by default will not allow site failover automatically.  Site failover will require Administrative intervention so you will be aware of this before it happens.  As a result the takeover is only done if you give GCO the authority to move the group while the link is down.

     

    The other item that you need to be aware of with an RDC configuration is TCP/IP related.  You have mentioned that you are running 4 NICs and 1 WAN link.  You have not mentioned how you are going to setup IP on the 4 NICs.  If all 4 links are on the same IP subnet, then Windows will only use 1 NIC for outbound traffic based on the order they appear in the routing table.  This is a function on how Microsoft implemented their TCP/IP stack and it cannot be changed by SFW-HA.  Multiple IP subnets can be configured if desired.

     

    Thanks,

    Wally

mikebounds's avatar
mikebounds
Level 6
14 years ago

 

As I said on previous post, even though the default for auto/manual failover is different between the 2, both can be configured as either, but GCO will take a lot longer to alert you a site is down.
Historically, VCS could not be configured for manual failover between sites and so async VVR was not supported (although I could never find an official statement for this in the product guides).  Now (from 5.1), VCS can be configured for manual failover between sites and therefore async VVR should be supported  (but you may want to clarify with Symantec).    Note you can change gabtimeout for heartbeats if the latency if too high between the sites, so using RDC should be ok from a technical point of view
Some other differences I didn't mention in previous post are
  • For GCO, you have to manually keep 2 main.cf's in sync, whereas for an RDC, there is only one main.cf
  • You need less NICs for GCO as you don't need private heartbeats, but note for RDC, you could configure 1 private heartbeat. VVR n/w as lowpri heartbeat and have a dual n/w for public.  Note, you probably shouldn't configure more than 2 heartbeats unless you have more than 2 independent links between the 2 sites.

If you have not configured GCO/RDC before, then I would recommend you getting a consultant to help you with design/implementation - Symantec should be able to put you in touch with Consultants in your area.

 

Mike