Cluster-based high availability tends to work by combining multi-ported disk
devices,
spare processing power, and a cluster manager (such as HACMP, MSCS, etc.).
When
a processor fails, the services that were running there (which could include
a DB2 "node"
aka processing "partition") are restarted in the spare processing facilities
(which may have
previously been idle, or may be already loaded processors that are set up to
absorb
additional workload in a failover). The disk resources associated with the
failed node
need to be accessible from the new node as well.
Disk (media) recovery is not usually part of this picture. Other approaches
are used
for that, including RAID/mirroring and database recovery (restore and
rollforward).
HADR (high availability disaster recovery), mentioned by Serge, is a log
shipping
database replication feature. Such products are typically deployed to
provide
failover to both different processors and different disks. This can be used
within
a cluster, with *separate* disk resources, which is different from the usual
configuration
meant when someone refers to cluster-based HA. More typically, log shipping
based HA is deployed between independent (not clustered) systems, either
within
one data center for "local" failover, or between geographically separated
("remote")
systems for protection against whole site failures.
Regards,
-steve p.
-------------------
Steve Pearson
DB2 UDB Development
Portland, OR, USA
"Daniel G. Cantua" <dc*****@co.la.ca.us> wrote in message
news:6c**************************@posting.google.c om...
We are thinking of starting to use clustering with our DB2 V8. I
understand that with clustering when a node goes down that the other
nodes will keep the database up for the users. What I would like to
know is does this include if the node has a hard drive crash and the
disks are not salvagable or just if the machine looses connection?
And if a new machine is used to replace the damaged one how does it
sync together? Any information on the subject will be appreciated.
Daniel G. Cantua
Los Angeles County - ISD