For shadow copy component backup with accelerator enabled, Maybe you would find that no matter whether to change data on disk volume, the shadow copy components backup job will send all data to server(optimization rate 0%), e.g.
Full backup, the optimization rate for the shadow copy components backup job is 0%
Not change data, full backup again, the optimization rate for the shadow copy components backup job is 0%
Change some data on each disk volume, diff backup, the optimization rate for the shadow copy components backup job is 0%.
Meanwhile, mabe you would find that sometimes the optimization rate is close to 100% no matter whether to change data.
Here is some explanation for it, hope helps.
Currently — we do not have any specific logic for Shadow Copy Components (SCC) or System State (SS) with regards to accelerator.
Whether or not we get any optimization cannot really be predicted.
The problem here is that we are not in control of the order of the items. This is different from regular file system backups. When enumerating the file system, we will sort the items in each directory prior to backing them up. This allows us to walk the track log and the file system at the same time.
The track log processing, assumes that everything is in a sorted order. Thus, when we process SCC (SS), things don’t necessarily align and we will not get any optimization. However, there is the chance that things will align and we will get optimization.
In other words, it may or may not work. Or, the behavior that you are seeing is expected.