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Re: hard disk terminology



Quoting Antoine Jacoutot (ajacoutot_(_at_)_lphp_(_dot_)_org):
> On Sunday 13 June 2004 10:18, Robert Storey wrote:
> > I'm just wondering if there is some technical reason for this. Why is it
> > impossible to create sub-partitions named /dev/wd0b and /dev/wd0c?
> 
> /dev/wd0b (b partition) is historically used for swap.
> /dev/wd0c (c partition) represents your whole disk.
> 
> >From disklabel(8):
> 
> disklabel only supports up to a maximum of 15 partitions, `a' through
> `p', excluding `c'.  The `c' partition is reserved for the entire physi-
> cal disk.  By convention, the `a' partition of the boot disk is the root
> partition, and the `b' partition of the boot disk is the swap partition,
> but all other letters can be used in any order for any other partitions

And commonly 'g' is used for /usr.

These are REALLY handy things to know when you
1) have a disk of unknown origin and need to see it (hey, I found this
   in the cabinet with a note: "Important, save.  May 3, 1994")
2) have your disk crap out.


You can use a/b/g on non-boot disks.  If you want.  B is always
risky if it's in a place where it might be treated as swap (bye
bye data).  This might happen if you have swap on your 15KRPM  sd2.
If sd1 dies and you reboot,  sd2 gets mapped to sd1.
I'm not saying that I've ever had disks shift on me and now "hardwire"
scsi3 -> sd3 all the time.
OpenBSD has a-p.  Most OS's have a-g.  You're not really limited.