A few days ago I created an encrypted volume on my DS411Slim and reported a major degradation in writing speed.
I hoped that reading was maintained in the original ballpark, but this is not the case.
12.5MB/s is all I can get and is very bad in comparison with the former 70+ MB/s

Since my first post I did some research and, according to Synology’s own tests, I should get about twice the current speed.

I’ll give a try at a more recent version of DSM (I’m on the stock 3.2) to see if it provides better performance.
I’m usually a bit reluctant to update the firmware of working devices, but the opportunity of getting better performance on the 50GB backups is pushing me in this direction.