external SSD not mounting properly after ungraceful shutdown

minnowahaw

Hey hi Giulio et alii,

For an installation project in a youth centre here in Antwerp - I am writing audio recordings to an external SSD (connected via the USB port of the Bela) from the Bela. I edited /etc/fstab so that the SSD is mounting automatically on boot:
/dev/sda1 /mnt/usb auto defaults,nofail 0 2
Until this everything is working supersmooth.

But what I didn't think through beforehand is that the youth centre shuts down the installation by pulling the plug. Because of this 'ungraceful', sudden shutdown the SSD regularly does not mount and files are not written to it (while the installation functions furthermore perfectly). Of course I understand that it's better to always gracefully shutdown, but in this context it will just happen that people pull the plug. I am now thinking about using an externally powered USB hub that I charge with a power pack - so that the SSD does not suddenly lose power when the plug is pulled. Could this be a solution in this situation? Or would there be any solutions in fstab or udev?
Thanks in advance for your answer!
All the best,
Sjoerd

giuliomoro

You can disable cache on the SSD, see: https://superuser.com/a/160186

This may cause excessive wear on the flash if you are writing to it in little fragments. Alternatively, you should be able to periodically call sync from the shell or fsync from C++ on the relevant file(s) and/or volumes.

minnowahaw

giuliomoro thanks for the swift reply, I will try that out!

minnowahaw

giuliomoro
so better not to use the disable cache method when recording audio to the SSD?
I write the audio from a buffer to the recording location on the SSD like this:
~rec_mono_buf = Buffer.alloc(s, 65536, 1); ~rec_mono_buf.write(~recording_location++~time_stamp++"_question"++(i+1)++"_recording.wav".standardizePath, "wav", "int16", 0, 0, true); ~diskout_recorder_mono = Synth(\diskout_recorder_mono, [\inBus, ~rec_mono, \recbuf, ~rec_mono_buf],~recGroup);

giuliomoro

minnowahaw so better not to use the disable cache method when recording audio to the SSD?

Well, that may depend on the actual flash. It may a minimum word size to write (e.g.: 8 bytes?) that prevents it from writing smaller values. As you are writing large-ish buffers, that shouldn't be a problem. Either way, it may be more efficient and less error-prone to call sync /mnt/usb every minute or so, instead of running entirely uncached. You could do that in a dedicated service.