RE: Exchange Server Redundancy

  • From: "Tiago de Aviz" <Tiago@xxxxxxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Mon, 8 Mar 2004 19:54:40 -0300

Jeez, what a complicated talk.


hey Jason, if you want simple replication of your Exchange server, check out 
CA's BrightStor High Availability Manager at <> 


It won't kill your budget ;) no need for shared storage or anything else. Just 
get a spare server or another server in your network, install exchange there 
and install Ca's BHB, and let it replicate. When the secondary server detects a 
failure from the primary, it'll stand-in in a matter of 6 seconds or less with 
the same name and IP Address.


Tiago de Aviz


(41) 340-2363 <> 


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From: Mulnick, Al [mailto:Al.Mulnick@xxxxxxxxxx] 
Sent: segunda-feira, 8 de março de 2004 18:16
To: [ExchangeList]
Subject: [exchangelist] RE: Exchange Server Redundancy

Microsoft implements "shared" clustering meaning that hardware resources share 
hardware.  This is a high-availability solution and not a fault-tolerant 
solution mostly aimed at reducing hardware and upgrade downtimes (upgrades as 
in service packs, hotfixes, etc).  Implementing an a/a/p cluster could 
certainly allow for a lot less downtime, but at a significant cost in terms of 
hardware/software licenses as you've noticed.  5x9 availability requires so 
much more than just the software and hardware it runs on, so I won't get into 
that in this thread.  Suffice it to say that 5x9's availability is a team 
effort that encompasses 8 layers of the OSI model ;-)


I for one would like to see the public folder replication scheme go away.  But 
for fun, let's assume that Microsoft did do that.  What would that mean in 
terms of availability that you can't get today?  A public folder replication 
interval is 15 minutes.  Cluster failover is ~ 10 minutes or less depending on 
implementation.  I'll take clustering over the public folder replication :)


There are software products out there that claim to be able to cluster the 
servers geographically and provide nearer to instantaneous failover.  I haven't 
seen them myself, and can't vouch for them, but I have a hard time 
understanding how they could be faster than a hardware failover and are 
certainly going to add cost.  


I think that understanding what the managers really want would be helpful.  Do 
they want fault tolerance, or just highly available messaging service?  If the 
latter, do they want to have the data that's in there all the time, or would 
they prefer the service to the data if it came to it?  Exchange does have the 
ability to offer "dial-tone" (although I've seen some flaky dial-tone so 
understand that Exchange can do better) service whereby if a store fails, you 
can wipe the store, restore service in the amount of time it takes to wipe the 
store and mount a new one with the same information, and then put the data back 
over time using the RSG option.  It's possible and can work for a lot of 
people.  VSS is another option that may be of interest to them.  Sounds like 
hardware failure is the most concern, and clustering is really a good option 
for that.  Gives a hot-standby host that automatically fails over in case of 
hardware failure reducing the time to heartbeat notification + time to bring 
the other node online or about 10 minutes depending on how implemented. 


Just my thoughts.  Glad you got it worked out.




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