Re: devfs patch v3
Richard Gooch (rgooch@atnf.CSIRO.AU)
Mon, 12 Jan 1998 07:36:03 +1100
Pavel Machek writes:
> Hi!
>
> > > where <H> is the host controller number, <C> is the channel number,
> > > <I> is the SCSI disc ID, <L> is the LUN.
> > > For a single partition it looks like this:
> > >
> > > sd_hHcCiIlLpP
> > >
> > > where <P> is the partition number. So, for example sd_h0c0i3l0p2
> > > corresponds to sdd2 on my system.
> >
> > Wouldn't it be better to use subdirectories as much as possible?
> > I know it will be more difficult to implement, but will make things look
> > nicer, readdir faster, etc.
> > What about
> > /dev/sd/hHcCiIlL
> > /dev/sd/hHcCiIlLpP
> > /dev/pts/N
> > /dev/scd/hHcCiIlL /* current cdrom code doesn't use partitions */
> > ...
>
> In case of devfs, only those who are actually installed take up space
> in /dev. Is that still problem? (I would not like to have /dev
> multi-directory, because it would make manual looking for devices
> harder (by one or more chdirs).) Hmmmm. Thinking about sunsite. That
> is I believe something like 50 scsi discs, and you probably have about
> 2 devices per disc (h...lL and h...lLpP), that's about 100 entries,
> which is perfectly ok. I think that even 1000 discs would be ok
> (altrough not good), since entries are in RAM and readdirs are not
> done too much, anyway.
You're assuming for large disc farms there are few partitions per
disc. That might not be true (maybe each user gets their own striped
partition).
Another point is that you still have to do inode lookups when you
first access a device, so with a flat directory structure the search
time is larger.
BTW: do you prefer SCSI discs in /dev or /dev/sd ?
Regards,
Richard....