Simply discussing various backup architecture options with customers can be a challenge, let alone actually settling on the best option for each environment. This tip explains the differences among backup architectures and what exactly is meant by the word "free" in some of those references. It will specifically address server-free backup, LAN-free backup and storage area network (SAN)-free backup.
The question you must answer is which "free" backup architecture is best for a storage set-up. The dilemma is understanding that "free" may not mean what you think it does.
LAN-free backup is backup that is done not over the LAN but either over the SAN or with a tape device directly attached to the storage subsystem, such as a RAID array. You might want to try this approach if you don't want to add to the load on your LAN and if all your storage is either connected to a SAN or concentrated in a few arrays. This approach is a popular alternative for systems with network-attached storage (NAS) filers.
In the case of server-free backup, the backup task is accomplished without the use of the server. The backup process is managed elsewhere in the system, often by software running on a switch in the SAN. This keeps the load off the server. However, preventing a single point of failure requires special consideration, because if something happens to the SAN, the ability to perform backups and restores will be severely compromised.
SAN-free backup refers to an architecture that doesn't use the SAN in the backup system. This could mean that backups are handled over the LAN, but more commonly it refers to a direct-attached storage (DAS) backup where the backup is connected directly to the storage array. This approach is most popular in highly centralized storage architectures where almost all of the storage is concentrated in a data center where trained administrators watch over everything.
About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. For the past 20 years he has concentrated on issues related to storage and storage management.