Hi Rich ! Commercial practice varies. The nicest HA solutions available today do require apps be "cloud" enabled, which is to say fully virtualized; you can then in-house them by building your own mini-cloud.
Choice 1 is whether storage is replicated or shared. Shared can be a cluster FS or a backend storage system (either of which should have internal redundancy). Choice 2 is running on OS-on-Iron or in managed VM's/cloud etc. Choice 3 is whether Apps run hot-hot, hot-cold, or hot-warm on the multiple nodes. For classical web apps, hot-hot load balancing is simple and effective - either with session state split between encrypted cookie and DB, or with sticky-sessions in load-balancer. Hot-cold failover with restart on 2nd server when failure is detected is annoying config management but perfectly doable, but must be configured for each app. We did a lot of this for legacy apps at my last shop. Veritas and each OS vendor have proprietary managers for this. Since they had multiple vendors there, Veritas was used. Problems with hot-cold is if App's shared storage is corrupted, it won't move; and since cold on node 2, the needed config there isn't always kept updated. If you make both your servers into VM hosts of any VM brand that allows load-balancing, and package each of your services into VM images, you can script auto(re)start of services. I note the upcoming BLU presentation in OpenStack, which is a one of many potential toolkits of possible use. - Bill _______________________________________________ Discuss mailing list [email protected] http://lists.blu.org/mailman/listinfo/discuss
