Re: San-Based replication VS DataGuard replication

macdba321 wrote:
> Group,
> I have a database at Site1 stored on a SAN, and a disaster-recovery
> site2 with identical hardware. They are connected by high-speed fiber.
> (Both SANs are enterprise-class with full journaling capabilities in
> case the connection were ever severed.)
>
> I am researching Pros & Cons of using DataGuard to keep Site2 ready
> for disaster time, VS letting the SAN manage keeping the two sites in
> sync.
>
> What are your opinions on these 2 methods?
>
> Thank you!!
> -mac

There is a place in an Oracle shop for both SAN based replication and Data Guard but the SAN based replication will NEVER better Data Guard if the point is to have a DR site: Here are just a couple of the reasons.

1. Data Guard checks what it replicates for internal logic. A SAN will happily replicate corrupt blocks.
2. Data Guard can guarantee zero data loss even when the data has not been written to a data file. You can not make SAN replication synchronous.
3. If SAN replication fails your primary will happily keep right on running transactions. Data Guard can be configured to bring things to a halt until the issue is resolved.
4. Data Guard, interestingly enough, is more efficient. What is being replicated is the transactions themselves not operating system blocks so are shipping less data. -- Daniel A. Morgan Oracle Ace Director & Instructor University of Washington damorgan_at_x.washington.edu (replace x with u to respond) Puget Sound Oracle Users Group www.psoug.org