Agent vs Agentless Backup
Posted by
Ed Tella on Wed, Feb 22, 2012 @ 11:22 AM
The term "Agentless Backup" has floated around the web for several years now, but lately it seems to be picking up more discussion. I did a little digging to figure out what all the hype is about.
Agentless backup technology does not rely on services running on the production machines to perform its backups. Instead, the agent is installed on a single machine that performs backups by monitoring the various TCP/IP protocols transporting packets over the LAN, (e.g. Telnet, FTP, CIFS/SMB, SSH, & HTTP).
Pricing Structure
Many vendors advertise simplicity in pricing and deployment with their agentless backups solutions. Agentless backup solutions that I have read about appear to be priced on backup storage size as opposed to the number of individual agents that back up devices. However, pricing based on the number of agents is generally accepted as the simpler option for small business and enterprise class businesses. It's for this reason that Datto offers the same pricing structure for our Agent Backup Solution, SIRIS & SIRIS Lite.
Key Issues
At first glance the concept of agentless backups all seems fine, but as I continued my research, I started to have some serious concerns with these technologies. One key issue that I recognized was that many agentless backup solutions are unable to backup files & folders contained within a virtual machine. Everywhere you look today in the IT world people are talking about the Cloud. What is one of the most important factors allowing this migration towards cloud computing? Virtual Machines. The use of VMs are becoming increasingly popular, and any business that utilizes a VM cannot go without backing up the files and folders that they contain.
Another key issue is that agentless backups frequently authenticate across the LAN using domain administrator credentials. The most common disasters I've assisted Datto Partners through have been in SBS environments or in Single Domain Controller environments. In these situations local DNS resolutions cannot be performed, domains are down and credentials seldom work.
Stability
In these particular instances, any agentless backup solution would become a nightmare during the recovery and BMR process. Conversely, a backup solution that uses an agent is far less likely to suffer hang-ups such as these at critical times. StorageCraft's agents, Shadow Protect and ShadowSnap, all authenticate as Local System on the machine. Local System has complete unrestricted access to the local resources of the machines and is not dependent on any external factors such as DNS failures & password changes.
Agentless backup solutions advertise many of the same offerings that agent backups deliver (such as automated backup verification, fulfillment of various compliance needs, ability for remote monitoring & management, and Exchange/SQL /SharePoint database "hot backups"). While these offerings match up well to agent backup solutions, the underlying process by which agentless backups are executed would not be something I would want my business to depend upon while trying to recover from an unexpected disaster.
When it comes to dealing with disaster recovery, one thing is always true: Each and every single disaster I've been through has been different, and they all had their own set of different factors. The worst thing about disasters is that more often than not, they strike when you least expect them. Having all the tools to recover readily available is the key to successfully overcoming any hurdles to maintaining complete business continuity.
Ed Tella is Documentation Manager at Datto, Inc
Questions? Comments? Send them to blog@dattobackup.com.
