Last October, I blogged about the vCloud Air DRaaS – The Good, Bad & Ugly in which I covered the following aspects:
- Service Overview
- vCloud Connector
- Test Recovery
- Failover and Failback
The main area which was lacking with vCloud Air DRaaS was failback. Failback could only occur offline whilst the virtual machine is shutdown. If we do the basic maths on a 50GB virtual machine on 100Mbps dedicated connection it would take 76 minutes.
Multiple this by 100 virtual machines then the numbers start to get crazy. It would take 127 hours or a little over 5 days to failback. Could you image saying to your Directors, sorry we need everyone to take a week off work whilst we failback?
For the sake of brevity the calculation is shown below. Overhead would be around 10% on 100Mbps link, giving 90Mbps throughput.
8Mb equal 1MB
50GB equals 51200MB
51200MB x 8Mb = 409,600 Mb
409,600 / 90Mbps = 4,551 seconds
4,551 seconds / 60 seconds = 76 minutes
100 VM’s x 76 minutes = 7,600 minutes
7,600 minutes / 60 = 127 hours
VMware understand that this kind of service was never going to be taken seriously by customers and could only be used for non production workloads and have announced some new service enhancements in a blog posted dated 20th January 2015. The enhancements are:
- Native failback support – provides seamless reverse replication from vCloud Air data centers to a customer’s environment, as well as support for offline data transfer via physical disk, to accommodate larger environments.
- Multiple recovery points – enables multiple point-in-time copies of replicated VM(s), allowing you to roll back to earlier snapshots of your data center environment in the event of corruption or the need to recover to an earlier set of data.
This is an excellent move by VMware as now DRaaS could become reality. What I would have hoped is that during failover VMware would have announced that they could offer virtual machine backups as part of the product offering.
Don’t forget DRaaS isn’t a panacea to fix application or service access for end users. The same rules apply to an on-premises solution as they do a cloud based solution.