I am writing to you, hoping you will be able to help me with the following problem (or at least point me in the right direction!).
The problem I am experiencing is, that the iSCSI link will fail on the Veeam backup server when I initiate a backup job.
Sometimes the backup job will run for a while before it fails, other times it seems to fail almost immediately after I start a backup job.
All backup jobs are configured to use direct SAN access.
When the iSCSI fails, the only way I can get the iSCSI link up again, is by restarting the server.
In the iSCSI Initiator I have 3 links defined (one for each volume in the SAN).
Only 2 links are used by Veeam; Volume 1 and Volume 2. Strangely it is only the connection to Volume 1 that seems to fail. The other links don’t seem to be affected, and backups from Volume 2 will work just fine with direct SAN access.
My setup is as follows:
Veeam backup 5.0 residing on a physical server with iSCSI connection through 2 stacked Dell PowerConnect 6224 switches, to a Dell EqualLogic PS4000 SAN.
Jumbo frames are enabled, and flow control set up in the switches.
Backup is taken from 2 vSphere hosts running VMware ESXi 4.1.0. Both hosts have redundant Gb iSCSI links to the switches, and redundant Gb Ethernet connections.
Backups are stored on a Synology RS810+. Throughput while backing up is roughly 70 MB/sec until direct SAN access fails on the Veeam backup server. After that it falls to roughly 35-40 MB/sec.
I hope that I have included enough information, and that you will be able to help me figure this one out!

EDIT: Images attached

