Re: Active/Active Site A/Site B using SRDF
- From: "John Darrah" <darrah.john@xxxxxxxxx>
- To: ryan_gaffuri@xxxxxxxxxxx
- Date: Tue, 3 Apr 2007 13:58:36 -0600
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, ryan_gaffuri@xxxxxxxxxxx <ryan_gaffuri@xxxxxxxxxxx> 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.
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