Exchange 2013 Reduction in IOPS over Exchange 2010

In Exchange 2010, passive database copies have a very low checkpoint depth, which is required for fast failover. In addition, the passive copy performs aggressive pre-reading of data to keep up with a 5-megabyte (MB) checkpoint depth. As a result of using a low checkpoint depth and performing these aggressive pre-read operations, IOPS for a passive database copy was equal to IOPS for an active copy in Exchange 2010.

In Exchange 2013, the system is able to provide fast failover while using a high checkpoint depth on the passive copy (100 MB). Because passive copies have 100-MB checkpoint depth, they’ve been de-tuned to no longer be so aggressive. As a result of increasing the checkpoint depth and de-tuning the aggressive pre-reads, IOPS for a passive copy is about 50 percent of the active copy IOPS in Exchange 2013.

Having a higher checkpoint depth on the passive copy also results in other changes. On failover in Exchange 2010, the database cache is flushed as the database is converted from a passive copy to an active copy.

    In Exchange 2013, ESE logging was rewritten so that the cache is persisted through the transition from passive to active. Because ESE doesn’t need to flush the cache, you get fast failover.

One other change is background database maintenance (BDM). BDM is now throttled back from 5 MB per sec per copy to 1 MB per sec per copy.

As a result of these changes, Exchange 2013 provides a 50 percent reduction in IOPS over Exchange 2010.

Exchange 2013 CAS HA with KEMP in less than 5 minutes

Yes you can setup your High Available CAS 2013 in less than 5 minutes if you have already done stuff on the exchange side. Let me tell you where it took most time for me to setup the Exchange 2013 CAS HA starting with my lab setup

My lab environment (built on MS hyper-v)

-1 Windows 2008 R2 DC
-2 Exchange 2013 CAS Servers
-1 Exchange 2013 Mailbox Server
-Domain setup as CAFÉ.CORP

Exchange 2013 CAS does not need to have a Layer 7 load balancer so it can be load balanced on the Layer 4. Below diagram shows how the setup was done for the Layer 4.

Kemp VLM Dashboard
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cas lb
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In the above picture-Do not get confused in the above picture with this Layer7 option; enabling it is a requirement to enable SNAT, which is a recommendation for Exchange 2013. Also make sure “L7 Transparency” is not checked.


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Here you can see the real server’s ip address which are CAS 2013 servers. Add them one by one.

That’s it – You are done with configuring the Exchange 2013 High Available CAS Server.


The image below shows that your both server are up and being load balanced.


 Didn’t I tell you it takes less than 5 minutes to setup A High Available Exchange CAS 2013 🙂



OWA is showing the VIP in the above picture



Things to remember and mistakes to avoid otherwise it can take hours to troubleshoot

-Takeout pen and paper and design your lab
-Note down the VIP
-Add DNS entry for the VIP e.g. mail.owa.corp point to while the real server ip 192.168.36 and for CAS1 and CAS2 respectively
-Point your autodiscover to the VIP
-Test both CAS server locally to make sure they are working
– All servers should be pingable and also the VIP


Last very important thing to remember while setting up the virtual NIC on the hypervisor makes sure you select the proper NIC for the VMs otherwise you will end up troubleshooting enormous hour. I thank for this to Bhargav who helped me figured this out.