Eric Seibert wrote an excellent comparison earlier this week on searchdatabackup.com reviewing disk-to-disk backup applications for VMware: Veeam, Vizioncore, PHD Virtual and VMware VDR. As beneficial as these products can be, however, they have a disadvantage when competing against array manufacturer products such as NetApp's SMVI that are specifically designed for backing up virtual infrastructure.
The primary challenge faced by software backup solutions is their inability to offload impact from hosts, a capability that becomes imperative as VM consolidation ratios increase. Applications relying on host CPU cycles and disk IO to facilitate backup compete for those shared resources with the production workload.
Most software backup tools rely on checksums of the entire VMDK to determine what data has changed and needs to be backed up – often a very IO intensive process that can even cause production applications to fail due to the resulting increased disk latency. According to Siebert's table, VMware VDR and Veaam take advantage of the vSphere vStorage APIs to utilize change block tracking. With the exception of Veeam running on a VMware Consolidated Backup (VCB) server utilizing change block tracking (CBT), software backup products require data deduplication, compressions and reads to transverse an ESX host − impacting the shared resources. And Veeam still requires a "copy-out" which produces far more IO than array-based snapshots.
Array-based data protection produces point-in-time copies without being IO intensive; it does not require walking the entire block set/file system/file structure every time a backup/replication occurs. Backup data can go directly to disk or tape without traversing the ESX hosts. Backups and restores consequently complete very quickly, and backups can take place more frequently throughout the day. NetApp's SMVI has yet another benefit in that it utilizes less storage since the footprint is deduped on both the production and backup datasets.
Utilizing different processes to protect and recover data for virtual machines, NAS content and any remaining physical servers – complicates not only backup, but also disaster recovery scenarios. Array-based solutions reduce complexity by eliminating the requirement to manage different replication schemes. Some of the array-based products further enhance disaster recovery by combining replication with VMware's Site Recovery Manager (SRM) to enable automated data center failover in the event of disaster.
The software backup manufacturers continue to add efficiencies and will undoubtedly increasingly take advantage of the vSphere vStorage API features to scale their products. Still, an off-board application/appliance will always be challenged to match the intelligence and efficiency of the storage array that owns the blocks (under VMFS) or file system (NFS). Array based data protection offers integrated backup and disaster recovery solutions that are both low maintenance and unified across the environment.
Russel Callen, INX Sr. Consulting Engineer, was a major contributor to this article.
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