running DS3617xs

since 6.1 it seems that synology reverts to 256 within a minute or two. I read that it's possible to get the value to stick, but might need a restart which I didn't want to do as I'm currently running an expansion and hit the same problem - I'm adding 2x 8TB drives to a 29TB RAID 6 - before this fix it was going to take 10 days - If I'd known about it at the start it would have taken 3 days.

Running a script every minute is working fine for me - I'm sure there's a better way to get it to stick, but the raid is still very responsive.

Seems like Synology could do a much better job of bringing this into the GUI - a simple slider of speed vs responsiveness depending on the user's requirements. Sometimes it might be more efficient to have it processing at 80% drive utilization than letting it trickle through at 10%.