In the last blog we talked about VMware vSphere HA and FT. As we discussed, vSphere HA is quite impressive in protecting against infrastructure failures at a reasonable cost. vSphere FT, on the other hand, has very limited use cases. However, none of these solutions are sufficient to meet high availability requirements for business critical applications with demanding service level agreements.
- Neither vSphere HA nor FT has application awareness. These technologies monitor just the container (the virtual machine). If an application or a resource that it depends on goes down, these technologies cannot detect and remediate the issue.
- Both technologies cannot provide availability during planned downtimes. If the application or operating system needs to be patched, the application will not be available to users.
- The remediation in vSphere HA requires restarting guest operating system that can be time consuming. This poor RTO may not be suited for enterprise applications.
This is where Symantec comes to rescue VMware vSphere administrators. Symantec has two products to fill these gaps so that organizations can confidently virtualize business critical applications. Thus you get to enjoy the agility and cost efficiency of VMware vSphere without compromising enterprise availability.
Symantec ApplicationHA: This solution solves problem 1 given above. Symantec ApplicationHA monitors designated application and resources (e.g. disk, volume, file system, network…). If a failure is detected Symantec ApplicationHA can restart the application and its resources in a pre-defined order. The application monitoring is quite efficient and foolproof. For example, if you are monitoring MS SQL Server, you can configure the ApplicationHA agent to login and logout from the database as if it were a regular database user. If the application restart fails (it can attempt application restarts for a configured number of times), Symantec ApplicationHA will send a trigger to vSphere HA (if available) to restart the VM on the same or on a different host.
Symantec ApplicationHA has support for over 21 business critical applications. Moreover, it provides a framework to create custom agents for homegrown applications as well. Symantec has been in the business of HA and DR for long time with superb reputation for HA agents.
Symantec Cluster Server, powered by Veritas: This product solves all the three problems stated earlier. This can work with or without vSphere HA. The application monitoring and remediation workflow is similar to that of Symantec ApplicationHA. In fact, the agents for both the products are the same. What is different about Symantec Cluster Server is its ability to migrate just the application and its resources to a standby VM as part of remediation. There is no need to wait for VM to restart thereby significantly reducing the downtime and improving RTO.
The ability to migrate application to another VM also mitigates the downtime normally incurred for planned activities like applying maintenance updates. You can update patches on standby node and migrate the application. Considering the long patching processes for modern operating systems, you definitely don’t want to deploy business critical applications on vSphere without the availability from Symantec Cluster Server.
Symantec Cluster Server for VMware is purpose built for virtual environments. When compared to traditional clusters like Windows Failover Cluster (formerly known as Microsoft Cluster Server), Symantec Cluster Server gives you high availability without compromising the perks of virtualization. For example, Windows Failover Cluster requires you to create VMs with physical RDM (raw device mapping) disks. If you use RDM, the flagship vSphere capabilities like vMotion, DRS, vStorage API based backups etc. are lost. Symantec Cluster Server has hot-plug APIs to work in VMFS and NFS based datastores.
Note: VMware has released product called vSphere App HA with vSphere 5.5 release. Lorenzo has written a great blog where Symantec Application HA and vSphere App HA are compared in detail. Check it out here.