I have been with Veritas tech support multiple times on this and gotten nowhere. We have BackupExec 15, version 14.2 and for the past year have had this problem- backups run slow... after they previously ran fast. The best way to illustrate this is as follows:
We have a hyper-v cluster. The backup server is on the same node and network as the fileserver in this case. The backup server is virtual, and the fileserver is virtual (I know that's redundant- just being clear). We have been going through these cycles where we rebuild the BE server and performance is great, then it tapers off and goes to tolerable, then abysmal. So we have two hyper-v nodes on a shared SAN array, and both machines are on the same node and LAN- that backs up to a Drobo 810 over iSCSI.
Two months ago, we backed up our fileserver, average data rate was 3500 MB/min. With no changes made, we ran the backup the following month and got 132 MB/min. I spent the month trying to get faster and couldn't. I built a new BE server and was back up to 3500 MB/Min. Veritas support has had us run their diagnostic tools and they keep saying the problem is a 1% drop across the network connection, and they keep saying the issue is the firewall, and they cannot point us to a problem on the server. Part of the problem with their diagnosis is that we turn off the Windows Firewall, and the network literally does not leave the hardware between the backup source and target servers, and then only leaves the VM to get to the storage.... plus the fact that rebuilding the server both on the same node, and on a completely separate hypervisor restores the performance. We are not backing up to tape, everything is to hard drives, and I am out of ideas. We have found that having multiple backups running simultaneously ridiculously exacerbates the problem- it will take a 3500 MB/Minute backup, then the second backup will run at 300MB/Min while the first one drops to 1200MB/minute, even on a fresh rebuild. To me this all points to a problem with the database or some issue within BE. Has anyone had a similar experience, and is so, how did you resolve it?