Impact of WAN Accelerator Appliances on Commvault Deduplication enabled backups and replication

Article ID: DD0021 Data flowing though a WAN accelerator appliance is analyzed and acceleration achieved by employing various data reduction techniques such as TCP flow optimization, deduplication, compression and caching. Commvault data flow using source/client-side deduplication is already optimized.

Symptom

Commvault Client Side Deduplication based backups and DASH copy performance may be impacted due to the WAN optimization appliances.

WAN (Wide Area Network) Optimization and Acceleration appliances such as Riverbed Steelhead® and CISCO WAAS® provide data transfer acceleration across WANs and are generally deployed at the end points of a WAN. Each packet of data flowing over the WAN is analyzed and acceleration achieved by employing various data reduction techniques such as TCP flow optimization, deduplication, compression and caching.  

Cause

Commvault software has the ability to optimize and reduce backup data before it is transferred over the WAN. Using source side deduplication, Commvault software on the source checks whether the data already exists on the target and transfers only unique deduplicated blocks across the network. Since the majority of the redundancy is eliminated by the Commvault software itself, there is very little additional efficiency to be gained by processing the Commvault optimized data stream through WAN optimizers.

Overall throughput of deduplication enabled backups and replication is directly dependent on WAN latency - faster the WAN, faster the lookups and hence higher the overall throughput of backup and replication operations. Introducing any additional WAN latency (Modification to hash checking process) has a potential of degrading the speed of WAN lookups and hence affecting the overall throughput.

Resolution

While WAN accelerator appliances provide significant benefit for most data types, they do not yield much benefit for already optimized and reduced data traversing the WAN and may introduce unwanted delays (latency).

Commvault testing has verified additional latency in Client Side Deduplication enabled backup and DASH copy throughputs with WAN accelerator appliances.

It is recommended that traffic is excluded from processing by these appliances for the following WAN scenarios.

  • Client Side Deduplication
  • DASH Copy

This exclusion process is vendor specific - please contact the vendor (Endpoint hardware provider) for more details.