DS411Slim overheating fix attempt #1

I’ve reported a problem with my nas a few weeks ago (here) and my plan to get it back to productive work in a reliable way.

As part of this plan I did order a OEM replacement fan: searching an equivalent model with the same small connector proved to be a waste of time.
After a few weeks it finally arrived and yesterday I picked it up at the shop and replaced it in the NAS.

The old fan had some substantial play in the axial direction and at low-speed failed to spin up, for this reason I had high hopes with the replacement.
It was a quick job requiring only 15 minutes and then I was ready to use the NAS.

Mirror rebuild worked fine, compressing a file with the PC CPU with source and destination on the NAS worked fine.
Active disks were at 43C and the CPU at 48C during the rebuild; a few minutes after it was completed the disks were down to 35C and the CPU at 43C.
With 19C of ambient temperature this is not an extraordinary achievement, but are manageable temperatures.

I felt confident, even if not overly confident, that the fix was going to work as desired.
To be sure that this was really the case and that the overheating was not going to hit me unexpected in the future I did a heat torture test by compressing a 140GB file using the NAS CPU instead of the PC CPU.

This time unfortunately the NAS did behave as with the older fan: after some time it died on me.
The latest reported CPU temperature in the web interface was 54C and it survived long enough to put a warning in the web interface telling me that it could not compress the file.
The NAS couldn’t be reached anymore (no web interface, no ping, no Synology assistant) and couldn’t even be restarted using the power button.

Next step will be to mount a heat sink on the current nonremovable stock heatspreader.
I have already found a suitable heat sink, now the challenge is to find the needed adhesive thermal pad.
I will lose the ability to use the 4th disk slot, but it is acceptable because future space expansions will likely come via a DS414slim for additional redundancy and performance.
And I still have the LS220D that can maintain some of the lower value data.

My DS411slim went south

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.