By all accounts, the architecture of VMware’s Consolidated Backup (VCB) has not kept pace with user requirements to maintain and improve backup and recovery objectives, capabilities, and costs as data centers become virtualized.
Wikibon estimates that less than 10% of VMware users implement VCB to back up their virtual machines.
Performance and server/storage costs imposed by the VCB architecture are the primary reasons. For example, VCB requires that the ESX server make a copy of the data associated with each VM in a sequential manner. In the case where 50 VMs share a physical host, this means that the ESX server will copy the files associated with VM1 to a separate storage area, then the files for VM2, then sequentially continue the process to VM50. Those snapshots are then mounted to a proxy server, on which the actual backup software runs. The penalty is both in terms of time (the sequential operation of creating the snapshots), and costs associated number of proxy servers required to backup a large ESX environment. For many users, the performance and storage requirements architected into VCB works against the grain as IT managers look to simplify their computing platforms and deliver increased value to business and application owners.
The good news is VADP (vStorage API for Data Protection) replaces VCB as a native API (no additional software required). VADP APIs integrate directly with certified backup software providers (e.g., CA ArcServ, Symantec NetBackup and Backup Exec, EMC Avamar, Visioncore, VRanger, IBM Storage Manager) and, among other things, enable you to remove a workload from ESX server by consolidating backup load and management onto a central backup server environment. Change Block Tracking (CBT) is also in the "good news" category for VM backup and replication efficiency. CBT enables the ESX server to determine directly what has changed between the source and target and then to copying only those changed blocks.
Action Item: Sunset your VCB infrastructure and begin the migration to VADP and CBT. Reallocate storage tied to VCB file and image snapshots back to the storage pool and reduce backup proxy server requirements to a single VADP API enabled backup VM within an ESX (not within the individual VMs hosting guest OS images and applications). Add VADP support and certification to your service level agreement with your back-up software vendor.