Hi All and happy holiday to all.
I wanted to test a new mobile setup recording long periods onto the attached hard drive and wondered if anyone knew if recording 16 tracks of nothing takes up the same amount of space on the drive as actual signal being recorded? I'm trying to get away, if I can, and not connect 16 mikes up for the test.

Why not check it yourself. Record some silence and for the same time amount record a tone on a different track. Look at the resulting file sizes. BTW it is a interesting question. 
 
Also my understanding is there is no such thing as true silence in recordings. Just levels so low that it appears equivalent. 

recorded as uncompressed WAV, yes

That's a great Idea, John and I wasn't aware you could record to compressed wavs. Wouldn't that slow down the I/O that could cause dropouts, pwalpwal?
I recorded a band who played and hour and a half set and all was going pretty good, getting good levels, I could see the WAVs drawing across the tracks but when I hit stop, I got an error message that went something like, 'Could not save file, disk full" and then all the wonderful WAV files went 'POOF'. I'm recording to a 1TB disk @ 44.1 so I was really surprised to see that. I thing, though, that it might have been I had edited where the default audio folder over to that disk, and I think it may have been caching to the C drive but, still, it had over 600 gig free. I think if I had just hit Ctrl + S after every song, I might have survived the night.
I'll test your suggestion, John, and post back later today.

Yes - recording silence to a wave file will use exactly the same amount of data as any other content so your test wI'll be fine. Variable bit rates are possible using other compressed formats.

RageoPari
That's a great Idea, John and I wasn't aware you could record to compressed wavs. Wouldn't that slow down the I/O that could cause dropouts, pwalpwal?
I recorded a band who played and hour and a half set and all was going pretty good, getting good levels, I could see the WAVs drawing across the tracks but when I hit stop, I got an error message that went something like, 'Could not save file, disk full" and then all the wonderful WAV files went 'POOF'. I'm recording to a 1TB disk @ 44.1 so I was really surprised to see that. I thing, though, that it might have been I had edited where the default audio folder over to that disk, and I think it may have been caching to the C drive but, still, it had over 600 gig free. I think if I had just hit Ctrl + S after every song, I might have survived the night.
I'll test your suggestion, John, and post back later today.

i think sonar will only record to uncompressed WAV? anyway, you don't want to compress anything until the final step, ie, as a delivery format

Yup, Tenfoot is right, no difference. So, I'll have to record an hour & a half but the wavs are now being written to my 1TB drive as I checked while recording and it's going up.
Thanks guys. I'm off to a holiday party
CHeers