Change StorageDevice to contain a data path and disk quota

[eflumerf]

No description provided.

[eflumerf]

Ensemble with
DUNE-DAQ/dfmodules#378
#40
DUNE-DAQ/appmodel#115

[glehmannmiotto]

added @gcrone as reviewer since he originally introduced the storage device class

[gcrone]

The original intent was that the StorageDevice class describes the physical hardware available on the machine. Should the quota and data_path be in a separate class defining how the StoarageDevice is used by the software?

[eflumerf]

My thinking here was that systems could have multiple StorageDevices (e.g. /data1, /data2, ...), and the only reason we would care about their size is if we wanted to impose a limit on how much of it a given Session could use at a time. If you look at the associated dfmodules, PR, you can see that this interpretation helps with setting up DataWriters to target specific StorageDevices

[gcrone]

I can see that the idea of quota and the actual data path are things that you want in the database. The point was that the StorageDevice class was meant to represent the actual hardware associated with a host and be used for purposes of CPU pinning etc rather than representing an aspect of the application that was using the device. I know we haven't made any progress on the hardware description / pinning aspects yet but it seems sensible to keep the 2 separate.

[gcrone]

Looks OK