This is the third in the series “everybody lies: backup”.  For the first two installments, see here and here.

Back in a simpler time – a few years ago -there were two types of backup vendors: those that used agents to protect computers and those that were agentless.  The backup vendors that used agents would promote the advantages of backup agents on the protected computer in terms of handling the specific capabilities associated with the operating system and applications; those backup vendors that promoted agentless backup would call out that without agents you had less maintenance because you didn’t have to install the agents.  The backup vendors that used agents would call out the security advantages for their own authentication mechanisms; the backup vendors that were agentless would note their security features for using what typically was simply a privileged username and password.  Backup vendors who provided agentless solutions would note that because they didn’t use an agent they had less impact on the computer being protected – agent-based backup vendors would scoff and discuss the load of the relatively “chatty” CIFS/SMB or other protocols that were used by the agentless backup vendors.

Every now and then I’d run across something that fell into the “lies” category – like vendors claiming to do source-level deduplication in an agentless manner – but for the most part exageration and not lies ruled the day.

Then came virtualization.  Once nice thing about virtualization is that the various hypervisors by and large support HOS (Host Operating System) backup.  Thus you didn’t need agents for each GOS (Guest Operating System) or VM (Virtual Machine.)  Well – you kind of didn’t.  Early VMware versions had issues with performing correct synchronization of applications for Windows – and some virtualization-only backup vendors built software for each agent that would correct (note: backup vendors that supported both virtual and physical environments had more flexible options.)

But this was the beginning of a trend that is still going strong – a trend I like to call “secret agents.”

Secret agents are the software that some virtualization vendors would put on the virtualization guest or host but claim that they weren’t agents but rather “infrastructure software” or some such.  It’s a game of semantics – just as Bill Clinton once famously questioned the definition of “is”, backup vendors would question the definition of “agent” and decide it was whatever they wanted it to mean.

It’s still going on today – where different vendors in the virtualization space make “agentless” claims but continue to put software at the HOS and GOS level.

Any backup lies you’ve heard lately?


  1. I wouldn’t mind if there was a Host OS agent, it’s the Guest agents that I don’t like. Host agents can be great for accessing the filesystem directly and streaming the data off after deduplicating. I don’t know if any do exactly that right now, but that would be the most efficient way. Putting an agent on each guest just creates more points of failure. Redundancy I suppose, as one guest could fail to backup but the rest would keep going; as opposed to the host agent not working and nothing gets backed up. It’s a tough call

  2. Great point – that’s why we offer both options so that each user can decide what’s best for their system.

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