File Servers Windows with very slow backup performance on HP StoreOnce 4700

[Mahmoud_Moussa]

We have a netbackup server which is 7.7.3 which takes backup from 4 file servers . 
The backup was going good enough and then suddenly started to have the backup window increased day by day until it reached a level where the backup is taking more than 24 hours and overlapping with other backup policies for other products.

we take this backup on HP storeonce 4700 . we have flashbackup policies on two file server and other windows policies on two other 2 file servers with the netbackup accelerator enabled based on archive bit .

There is one thing that I have noticed and seemed very strange is that in the client properties the archive bit is enabled and not the time change , however in the job details view the logs say the opposite , the archive bit is disabled . 
I don't know if this point have an effect here , 

We're running the storeonce on low bandwidth mode as recommended and the accelerator is enabled

so are there any suggestions here ? where to start from investigating this issue ? are there any special logs to be enabled so that we can have clearer views on the problem ? 

Appreciate your assistance

[Michael_G_Ander · Accepted solution]

What is slow ? And how does it compare to the infrastructure you running on ?

The usually performance benchmarks are

1. How fast can you read data (bpbkar32 null test)

2. How fast can you transfer data (usually iperf or similar tool)

3. How fast can you write data on the backup media (usually bptm log)

Also pretty sure that accelerator does not work on archive bit, but with a tracking log which can be based on the journal.

[Mahmoud_Moussa]

Thanks a lot Michael , 

  Your points have guided me to understand where to start from and how to track down the slow performance bottleneck 
Thanks for your guidance 
We now have a better performance but still the customer looking for more improvement 

Thanks again