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The CPU hit on the ESX server is minimal. And the I/O hit on the storage is also minimal, as all it has to do is take a snapshot and then perform a smart, block-level incremental of today's new blocks by replicating them to another system. (Note that this block-level incremental is being done by the storage that already knows which blocks need to be copied, so the I/O impact is as low as it can be.) Vendors that offer these capabilities have their own ways of providing file-level restores from these backups as well.
Dell EqualLogic systems, because they're iSCSI, can communicate directly with the virtual machines via IP to coordinate the snapshots. FalconStor has agents that run in all your VMs to coordinate snapshots and do the "right thing" for a number of applications. NetApp uses VMware tools to do snapshots; however, NetApp's truly unique trait is that it can dedupe VMware data -- even live data. Think of all of the redundant blocks of data you can get rid of by using the deduplication tool included with NetApp's Data Ontap operating system.
Bottom line for VM backup
There are a number of technologies you can deploy today to make VMware backups better. However, many of them are still saddled with disadvantages, especially when compared to traditional backup processes. Perhaps the best current alternative is to move your VMware instances to VMware-aware near-CDP-capable storage. Or maybe VMware will solve some of these backup problems with
BIO: W. Curtis Preston is an executive editor in TechTarget's Storage Media Group, as well as an independent backup expert.
This was first published in August 2009