As we know, Symantec VBS provides start-stop, fault-management and disaster-recovery capabilities for business services with multiple tiers running in heterogeneous platforms e.g. database tier running in AIX, application tier running in Solaris, web tier running in VMware VM.
However even if your environment is not heterogeneous, Symantec VBS can provide significant value. In this article we’ll explain the use cases provided by using Symantec VBS in pure VMware environments.
We’ll explain each of the use cases with the help of the following example.
Consider a business service pertaining to employee records, with two tiers running in VMware virtual machines. The database tier is running in a VMware virtual machine hremp_db _vm. Web-Tier is running in a VMware virtual machine hremp_web_vm.
1 Flawless Application-Aware Start-Stop of Business Service running in VMs
Let us assume that the application tier running in hr_emp_webvm cannot display employee records if the database tier has not started and initialized fully. Given this requirement,
the ideal order of starting the business service should be :
- Start hremp_db_vm.
- Start the database tier.
- Wait for database tier to be initialized fully.
- Start hremp_web_vm.
- Start web tier.
To achieve this you do the following.
- Install and configure ApplicationHA on hremp_db_vm.
- Install and configure ApplicationHA on hremp_web_vm.
- Configure the database tier in ApplicationHA. Assume the database tier is represented as a service group named DB_SG in ApplicationHA.
- Configure the web tier in ApplicationHA. Assume the web tier is represented as a service group named WEB_SG in ApplicationHA.
- Create a Symantec VBS with DB_SG and WEB_SG. Configure a soft dependency with DB_SG as child and WEB_SG as parent.
- Configure “VM Start” and “VM Stop” for both service groups.
- Start/Stop the VBS
With VMware native solutions, this requirement is addressed by the vApp feature. However consider the following limitations of vApp.
- vApp has no application awareness.
- vApp uses timeouts to allow tiers of a multi-tier application to initialize. These timeouts can affect the start-stop time if overconfigured (greater than ideal value) and cause failed starts if underconfigured (less than ideal value).
2 Fault-Management of Business Service running in VMs
Let us assume that that if the database tier becomes unavailable for some time and later becomes available, the web tier which lost connection when the database tier became unavailable is not intelligent enough to reconnect to the database tier.
So the requirement here is that when the database tier becomes unavailable and later recovers, one needs to bounce (restart) the web tier so it reconnects to the database tier.
To achieve this, you simply change the dependency between WEBSG and DBSG to type “Restart”.
3 Using VBS for End-to-End Disaster Recovery of Business Service running in VMs with Application Awareness
Let us assume that in order to do disaster recovery, user has configured data replication of the data disks from primary site to secondary site. To provide failure detection and failover management, user can configure ApplicationHA with GCO inside the virtual machines. Please see the following figure.
VM Image Replication
Currently VBS DR is not supported for the case where VM Image is replicated.
Video Showing VBS Configuration and Operation in VMware environments (courtesy:Lorenzo Galelli)