Automating site-to-site failover
I am looking for a system that can switch automatically from one site to a backup site but with standard hardware and without modifying the applications (no clusters like MSCS or HACMP). I think it's easy enough to boot on a virtual disk that is on an EMC CXxxx, HP EVA or IBM FastTxxx and to have a clone of this virtual disk on a remote site.
However, in the case of a disaster, I haven't found any product that can decide to start a server on the backup site automatically or by simply going back to the initial site (data and servers) when the problem has been solved.
Do you of any products that can do such things?
In part because I work for a vendor, -- full disclosure: I work for
-- I try not to recommend specific products in this space. But since you asked the question so directly, I will do my best to answer.
You don't explain your reluctance to "modify" applications. To the best of my knowledge, MSCS and HA/CMP don't require you to make changes to applications in order to cluster
them. MSCS may make some changes on its own but it doesn't make significant changes.
You can certainly do what you are looking for with VERITAS Cluster
Server with the Global Clustering Option. VCS will enable automatic (or semi-automatic; more on that in a minute) failover
from site to site and does not require application modification. Of course, for site-to-site failover to work, you need a way to get the critical data from one site to the other. The best way to do this is with a data replication product, such as VERITAS Volume Replicator, Hitachi TrueCopy or EMC SRDF.
The issue with automatic site-to-site failover is that performing a
site-to-site failover can be an expensive proposition and generally, it's something that you don't want to do by mistake even once. My advice is that you make sure that whatever tool you choose requires some -- but minimal -- human intervention to complete.
Beware of setting too many vendor requirements for achieving a useful and worthwhile goal such as site-to-site recovery. Such requirements may be unnecessary and may disqualify many solutions that could otherwise help you.
Evan L. Marcus
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This was first published in March 2004