We use CommVault but will soon switch to NetApp's SnapManager (since we're switching to NetApp storage). Veritas NetBackup may still be a good choice for Enterprise backups (haven't used it in a decade). Legato used to be a chief competitor to Veritas. It's now owned by EMC and known as EMC Networker. Don't know if there's a dependency on EMC storage like SnapManager
When you say database server, which database will you be using for ArcGIS Server? If Oracle, consider writing, or having someone else write, a few simple RMAN backup scripts. RMAN is free with licensed Oracle servers and CommVault mostly provides a GUI and writes the RMAN scripts for you. CommVault, like most Enterprise backup software I suspect, is expensive. A friend recently saved his organization 100K by dropping CommVault to back up Oracle servers using RMAN scripts. I believe the total cost of CommVault licenses, including all database agent licenses, equaled or exceeded the entire cost of the org's SAN storage (several hundred thousand dollars). If you really need a GUI for Oracle backups, use Oracle Enterprise Manager.
Be mindful with Enterprise backup software that you will typically pay extra for database vendor-specific "agent" licenses (e.g. Oracle, SQL Server, etc) to perform hot/online backups. Carefully consider your backup requirements and choose something that meets, but doesn't grossly exceed, the business need. Don't buy a Cadillac if a Corolla would do. There can be a risk to underspending as well--sometimes you need a Cadillac. Your requirements and business need will help guide the purchase.
I'm not presently a backup or storage administrator so that's about as much input as I can provide. I am, however, very interested in NetApp's Snap Manager. This is what we're replacing CommVault with for both SQL Server and Oracle backups. I'm wondering, and don't yet know, if there's also a per-server database agent license cost for Snap Manager. Anyone here use it?
Agent costs can add up fast. I'm sure Snap Manager has some wonderful features. But I don't know if they meet a specific requirement. In some large IT organizations, certain purchases can be a foregone conclusion made by one part of the IT Enterprise without consulting other parts of the IT Enterprise. And then you're stuck with it and "must" use it because it is The Standard. If you don't have to plug-in to the rest of your Enterprise's backup regime that gives you a lot more flexibility.
Good luck and please let us know how it turns out.