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Re: Active/Active Site A/Site B using SRDF

From: John Darrah <>
Date: Tue, 3 Apr 2007 13:58:36 -0600
Message-ID: <>

I believe the term people like to use for the active / active SAN replication is stretch cluster. They have pretty ridged distance limitations (20km comes to mind), require a fat pipe and a network glitch will bring both sites down to avoid a split brain situation. Someone feel free to correct me if I got anything wrong on this. Look into Oracle data guard, it has features that can do a lot of what you are looking to implement. There are products that can give you HA at your load balancers *BIG-IP
Global Traffic Manager for one.*

On 4/3/07, <> wrote:
> The SAN/Systems Administrators claim its possibly to have a Site A/Site B
> setup(at two locations). Use SRDF asynchronously to populate and keep both
> sites active.
> 1. I don't think its possible to actually write to sides(2 different
> databases) and still maintain transaction control? So at a minimum you write
> to just one site and then populate the secondary site.
> 2. If both sites are active and the population of the second site is
> asynchronous that implies that the second site will be slightly behind so if
> users query both sites then one user may get an inaccurate picture of the
> database.
> 3. Is it possible to have active/active with a synchronous SRDF? I would
> think that would affect performance. Since you can't end the transaction
> until both sides are applied.
> 4. I would think the better solution is to havea primary and failover
> with the load balancer having an exception handler so when Site A goes down,
> failover to site B.
> 5. If you want to use both sites to query, then you are better off
> identifying performance intensive queries such as reports and use the
> secondary site as a reporting database(unless Site A goes down, then site B
> handles everything)
> Even with all this you still have a single point of failure at your load
> balance since its the entry point or is there a way to multiplex this?
> This is long... not sure how to summarize this.

Received on Tue Apr 03 2007 - 14:58:36 CDT

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