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

  • From: ryan_gaffuri@xxxxxxxxxxx
  • To: mzito@xxxxxxxxxxx, <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 04 Apr 2007 13:05:23 +0000

I think the original plan is to actually have two sets of database files on two 
sites. I dont see how that can possible work with oracle unless there is some 
kind of two way mirroring you can do with a SAN across a fibre, but I doubt it. 

-------------- Original message -------------- 
From: "Matthew Zito" <mzito@xxxxxxxxxxx> 

EMC SRDF does not support active/active with neither synchronous nor 
asynchronous configurations.  When you have an SRDF environment your R1s (near 
side) are writeable while your R2s (the far side) are not.  

If you want to do active/active sites, you can do a RAC stretch cluster using 
either long distance Fibre channel (bleh) or iSCSI (much better), or you can do 
things at an application level.  


From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of ryan_gaffuri@xxxxxxxxxxx
Sent: Tuesday, April 03, 2007 12:39 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Active/Active Site A/Site B using SRDF

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 
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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