Storage IO Mismatch

On its face, this looks like a great idea – backup storage also facilitating near instant VM recoveries. But the challenge is most disk backup appliances are tuned to handle backup workloads, not the random IO that production applications produce. The other issue is that most disk backup appliances are designed for storage capacity efficiency. They are often configured with high density (4 TB) drives that run at slow (5400 RPMs) speeds. Between these two factors, the added latency could make for very poor application response times.

Lastly, many disk backup appliances are now using some form of data deduplication. While this is a great way to efficiently store backup data on disk, if deduplication processes are running while production data is mounted on a disk backup appliance, storage IO throughput may come to a grinding halt. Especially when the above two factors are also in play.

Balanced Hybrid Backup

One way to circumvent these issues is to consider low cost storage technologies that provide a mix of SSD resources along with high speed disk drives. Some of these offerings are similar to the hybrid flash arrays on the market but are available at a fraction of the cost. These systems can be used as a disk backup target to facilitate rapid backups while also serving as a platform to support data recovery-in-place capabilities. For example, a small portion of SSD could be allocated to backup data for business critical VMs. That way if a VM needed to be quickly recovered, this area could be used to support production workloads and the above latency issued could be avoided.

These storage systems could also be used in conjunction with existing deduplication disk backup appliances. Backup managers could stage certain business critical data sets to the hybrid array first and then schedule a secondary backup job to the dedupe appliance to support extended retention on disk.

Reference: http://storageswiss.com/2014/06/04/making-virtual-server-recovery-in-place-viable/