It was a while that I was traveling quite a bit and giving little attention to my home NAS.
It was getting stuck from time to time but I was not really worried.

For Christmas I had some spare time and decided to do some much-needed backup: the notebook to the NAS and then the NAS to a USB disk that I usually keep disconnected to be on the safe side.

Things did not work out as planned because the DS411Slim was not running long enough for me to complete even the first step.
Status led a solid blue, network led blinking, but no data movement at all and it will not shutdown using the physical button.
Only way to restart the NAS was plugging the power and as you know this is not the nicest thing to do to a disk with data being written to it.

I did it once.
I did it twice.
I did it one time too many and got the status led blinking nonstop.
Not good.
One of the disk’s metadata was corrupted and the mirror diskgroup in degraded state.

Situation was bad but not tragic: I decided to reverse the order of activities and do the NAS backup first using the disk still working.
This worked fine.
Then I decided to hack the fan control file to make the fan spin faster as suggested in and then did the notebook backup using from Microsoft.
This worked fine again.

I felt all my problems were fixed, but I was soon proved wrong.
Due to the scarcity of space on the share I decided to let the NAS compress the .vhd file by issuing the command through the web file manager and I got hit by the CPU overheat issue again even if the fan was clearly spinning (relatively) fast.
I did another try at the compression after restarting the NAS and it went down again: cpu in the web interface appeared to be in the 52-53 celsius last time I checked before going to sleep, but in the morning the system was stuck again.

I have almost alternatives: I have to mod the device.
One option is to replace the fan: maybe it just got tired after a few years and can’t spin as fast as it should.
Another option is to use a thermal adhesive to attach a finned heat sink to the CPU: the heat spreader (irreplaceable) is absolutely untouchable (I mean burning) when the system is blocked hence it can clearly benefit from a better heat dissipation.
Before I go down this road I need to have a failsafe solution hence I ordered a cheap Buffalo LinkStation 220 with a pair of 1TB disks where I will copy all the content of the Synology.