I'm tring to backup Cluster file server
Two cluster nodes are configured as SAN Clients
The policy is configured to backup the clustername
the backup selection is one partition of 3T (most of it MS Office files) every 2 weeks and daily diff-incremintal backup
the daily diff-inc backup takes 11 hours
Some times backup speed less than 10 Mbps
why so slow?
One word: fragmentation.
This is causing slow read speed from disk.
Invest in an online defrag tool.
In the meantime, break down the Backup Selection into smaller chucks (start with 4 streams) and multi-stream them.
We have been able to cut down backup time for customers by breaking up the volume into multiple streams. Something like this (At one customer from +- 36 hours down to 8 hours) :
Assuming a Windows cluster, increasing file cache and maybe page file some times help with the speed of reading files from the volume(s). Journaling might also be worth a look, for the incremental backups.
Talk with your SAN administrator, as there might be something that can be done in the storage system. Higher tier, prefetch, bigger procent read cache, etc.