'device' representation in the filesystem questions
Robert Bonomi
bonomi at mail.r-bonomi.com
Wed Nov 14 23:37:32 UTC 2012
it appears that FreeBSD, at least 8.0 and later:
a) no longer uses 'raw' devices for anything
b) no longer uses 'block' devices for anything
c) randomly assigns device 'major' numbers
d) doesn't use device 'minor' numbers for anything.
e) as a result of c) and d), there is no way to
establish 'device' physical characteristics
from the 'node' information.
Is there a wizzard who can confirm/deny?
Or, if there's a better place to ask, can anyone point me there?
There are significant performance and 'addressability' issues when doing
i/o directly to 'fixed block' devices, especially 'write-once' media.`
The classical 'block' device type was a reliable indicator of 'fixed block'
behavior, how does one make that determination today?
Is there any way to get 'classic' mag-tape behavior -- where, for example
a read(2) returned the lesser of the bytes in the block, and positioned
to the beginning of the next, regardless of whether the etire content of
the current block had been read ?`
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