top 2 waitstats on one of the server are BackupBuffer and BackupIO. The backup is being done at a network location using symantec backup utility. There are around 20 databases with transaction log backup scheduled to occur at 30 min interval. Does that mean that I need to add storage to the server or to the network location where the backup is being done.
I have had fun with NetBackup and Backup Exec in the past 🙁
You don't say whether you are seeing a problem in terms of backup throughput or not.
Have you tried performing a native backup direct to the same network location for comparison?
There's a process to go through to determine where the bottleneck is.
There's some excellent advice in the following White Paper, documenting how a 2TB database was backed up (very) remotely in 34 minutes:
http://download.microsoft.com/download/d/9/4/d948f981-926e-40fa-a026-5bfcf076d9b9/Technical%20Case%20Study-Backup%20VLDB%20Over%20Network_Final.docx (Word document - well worth the download).