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Taneja Blog / Data Center Systems / Software Defined/Virtualized Infrastructure

Virtualized applications - how do you protect uptime?

Did you know that you might not get quite the availability and capability you want from a typical virtualization initiative, even if you're planning for mission critical applications?  The reality is that VMware goes pretty far, and delivers vast improvements in availability over non-virtual infrastructure, but you can do a little better, and you might want to do a little better for critical apps. 

When we talk to end users, and we hear frequently two drivers for virtualization. 1. Customers want to decrease their TCO, and virtualization can do it.  2. Customers want better IT capabilities, and many things can fall into this bucket.  When we survey customers, these two reasons are the top drivers for 90% or more of the respondents.

In terms of #2 above, the capability that customers most often identify as most important is business continuity.  But in this particular dimension, VMware doesn't always give customers what they expect out of the box.

Out of the box, VMware vSphere gives you great capabilities like vMotion, DRS, and ESXi clustering.  This can help pool resources, automate the placement of workloads, and make workload movement across a cluster pretty easy.  In turn, customers can move workloads around when they need to have planned outages to service or replace hardware.  With shared storage and in the event of unplanned outages, customers can also easily restart virtual servers on another system.  That's a pretty big improvement over the days of standalone servers, and can help make the business much more continuous.

Even better, for truly critical applications, VMware also offers an HA solution.  HA can monitor a virtual server, and when a heartbeat is no longer detected, can trigger the automatic restart of that virtual server.  If you're working in a cluster, that will happen on another hypervisor if there was a hardware failure.

But the reality is that VMware HA doesn't detect the majority of failures - application failures most often happen not because of a halted server, but because of application errors or server configuration errors.  Moreover, I've heard that VMware HA also restricts the use of some host settings (haven't actually investigated in the lab yet).  Most importantly though, VMware HA restarts can take a good 4 or 5 minutes.  These are drawbacks that may fail to meet your requirements for critical applications.

Over the past few weeks, I've been engaged with Symantec on a multi-fronted conversation around business continuity, and I've gone so far (along with Don Harrop) as to take a look one of their recent product offerings in the lab to validate their claims around how it delivers better availability.

So what did we find in our testing?

VCS speeds up failover events to the point that continuity is maintained. VCS patrols application integrity, and fully protects the viability of that application. Instead of running the risk of hung applications, and minimally tolerating 5 minute or more outages, a stateful app can resume with less than 45 seconds of outage, with very little overhead in exchange for the protection - and that's a key point - that very little overhead makes VCS efficient.

Now the final interesting angle I'll call out here is that Veritas Cluster Server actually speaks to the number one reason why customers pursue server virtualization too. If you remember what I said, I said this was TCO savings. The biggest factor in achieving TCO savings with virtualization is efficiency, achieved through the consolidation of workloads and higher VM density. Symantec has a message here too. The Symantec ApplicationHA and Veritas Cluster Server solutions deliver enhanced availability while sharing resources and enabling low utilization standby systems with less overhead than full clones running as standby servers, and other potential approaches.

VMware channel partners have all recently heard that virtualization comes with great demand for other complementary services, software, and hardware. Customers know this already. Well business continuity is one such area, and it is particularly important as virtualization begins to take on increasingly critical enterprise workloads.

So if you're looking for what other componentry you're going to need to bring along, you should turn some attention to DR, and as I've stated in the test report, take a look at Symantec's VCS as a clearly differentiated product. 

Full report is available here, or here.


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