Tuning the filewalker

This is a subjective observation, but my HP Microserver Gen7 started being much more responsive after I added more RAM. The box handled ~12 TB of nodes at the time with 2 GiB of RAM, I changed that to 16 GiB. I wouldn’t be surprised if the same was with a Synology device.

Could you try defragmenting your directories using e2fsck -D? This was suggested before in another thread, it would be interesting to see if it helps in your case. This operation likely requires downtime though, as the file system cannot be mounted during the process.

On my Microserver the file walker takes around 8 minutes per TB in a similar setup (ext4, no RAID, noatime, no caches, etc., with probably the only difference being I’m setting the inode size to 128 bytes)