Choosing a backup software

Before choosing a backup software, you need to consider the following and even more:

• What is your RPO? (recovery point objective)
• What is your RTO? (recovery time objective)
• What type of backup are you requiring, Full, Weekly, Incremental, Off-site?
• What is your backup time window? (Can you fit your backups to it?)
• How many servers do you want to backup - How much data? (Buy a single backup
  server or a server with a media server)
• Will they be supported by the backup software? (OS and application)
• What is the average daily data change? (Full every day or incremental)
• What is your growth prediction?
• Do you have more than one site to backup?
• Are you buying a new backup server or using an old one? (Check hardware
  and OS compatibility lists)
• Are you migrating from an old backup program to a new one? (Keep the old
  one alive? for how long?)
• Backup to tape or disk? (simple disk or a Deduplication disk?)
• Is the data on NAS devices or servers? (What vendor? - check support matrix, needs
  NDMP license)
• How many virtual machines are you planning to backup? (Network backup or SAN backup)
• Are your virtual machines VSS aware?
• Will your backup program be able to truncate the virtual machine log? (SQL, SharePoint, Exchange)
• Does your virtual machines contain physical RDM (VMware) or pass through
  disks (Hyper-V)? (You will need an agent)
• Do you have a virtual cluster? (Virtual center - VMware, CSV - Hyper-V)
• Some virtual machines are actually an appliance - Their vendor should supply a
  way to back them up.
• Have you got a DR site? (Backup the DR servers, allow quick recovery on the DR site,
  additional hardware)
• What kind of support are you looking for? (24x7, 9-17 etc.)
• What is your budget?

Don't forget the most important rule of backups: Restore!

The following links will provide you with a starting point and will show you the trends of the
enterprise backup software community:

List of backup software (Wikipedia)

Gartner 2015 Magic Quadrant for Enterprise Backup Software and Integrated Appliances (June 2015)

Gartner 2015 Magic Quadrant for Deduplication Backup Target Appliances (September 2015)