Exactly this was the question. If several devices fail at the same time and you look for the course you might get suspicious.
 
Anyhow,
 
the NAS is working again. I assume this was only a temporary alert. I cannot trace the alert back to something special. One could do a S.M.A.R.T oft he HDDs to read out their status.
 
The bad new ist that the NI PXIe-1075 (crate) power supply seems to have a failure (95% sure). It is in a shuttle unit and can in priciple be replaced as a whole.
The shuttle itself is not easy to open itself, so to really measure the voltages is diffcult/takes some time. I tried to measure the voltages at an external connector (DB9 at backside of the crate) but as 
you might know it doesn’t have a „hard switch“ but some push button that starts some logic. Depending on the number of modules in the crate or if I switch on the fans on full intensity (as a load) the 
power of the crate immediately switches off or stays on a little bot longer. If you take out one or more modules (no particular one) the crate stays on a little bit longer. Some of the modules show an 
error then. I assume is because of wrong/missing power.
Again, I had no chance for a careful measurement of this behaviour, so I am not fully sure whether I am right.
 
Unfortunately, the crate itself cannot be bougth anymore (discontinued), similar ones are incredibly expensive and also usually not on stock
 
I suggest a twofold strategy :  We can bring the „power supply shuttle“ (that i shte name) to a specialist here at GSI, may be Shahab knows someone (or Jan/Uwe). May be there is a quick way to fix it.
In former times weh ad someone here at GSI.
 
Or try to get a new power supply shuttle (but it might be discontinued as well).
 
The full replament part (someone would need to contact NI and/or search the net, if a company/ebay still has it) is called:
 
„PXIe-1075 PowerSupplyShuttle“
I found two part numbers for it:
198136B-01L (original part number ont he back of the deivce)
780292-01 (official replacement part number) . However, NI doesn’t know about it on the web page.
 
http://download.ni.com/support/manuals/372539a.pdf
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019N2CSAU&l=de-DE
 
Evtl. hier anfragen:
https://www.rosenkranz-elektronik.com/de/messgeraete/273795/national-instruments-ni-pxie-1075
 
or datatec, they also have a lot NI Pxie stuff.
https://www.datatec.eu/pxi-chassis
 
ebay?
 
However, again I am not 100% sure about the PS, but there are strong hints.
 
A few notes at the end:
 
Although none of the below is likely the reason for the failure, yet,
 
If a label on crate a states „please leave some headroom for ventilation“ then please do it. There might be a reason.
Please consider the maximum power that can be drawn from a single mains connection. Two crates (NIM/NI) + a server computer are quite something, in particular on a multi-outlet power strip….
Bending of cables, in particular of optical fibres… Don’t bend them two tight. The NI optical cable can also not be ordered anymore. Stiff long cables on tiny connector (found on several places on the NI 
crate).
 
I cannot take further care about the issue since I am pretty busy here with the Etarget beamtime but may be it helps soemhow.
 
Best,
 
Carsten