disklabel differences FreeBSD, DragonFly

Matthew Dillon dillon at apollo.backplane.com
Sun Jul 30 17:01:06 UTC 2006

:>>>>> "Dmitry" == Dmitry Marakasov <amdmi3 at mail.ru> writes:
:Dmitry> * Matthew Dillon (dillon at apollo.backplane.com) wrote:
:>> felt that 8 partitions is restrictive.  My main home server has 10
:>> and the main DragonFly box has 11.
:>> There is another solution for FreeBSD folks, however.  You *DO*
:>> have four slices to play with.  You can put a disklabel with 8
:>> partitions in it on each one (for 32 total).  It isn't as
:>> convenient, but it does work.
:Dmitry> About `lack' of partitions - don't forget that labels can be
:Dmitry> nested.  Just do `bsdlabel -w /dev/ad0s1e` - you'll get
:Dmitry> /dev/ad0s1ea.
:Don't also forget that gpt(8) exists and seems to provide for large
:numbers of partitions.  It even seems to be compiled into GENERIC by

    Yah, well... I'd be a bit leery of using anything more complex then
    a basic disklabel.  The more complex the setup, the more likely that
    a disk crash will become unrecoverable.

    I had an issue a little while back with a disk crash where the OS's
    insistence on reading numerous sectors at both the beginning and
    end of the disk before 'recognizing' it as a disk prevented me from 
    being able to access the disk at all, even when all I wanted to do 
    was to make a disk image of e.g. '/dev/ad6' and skip over the bad
    sectors.  It pissed me off so much I rewrote the code in DragonFly to
    not actually try to interpret a slice or partition table unless something
    needing the slice or partition table was accessed (like '/dev/ad6s1').

    A linked or recursive partition table makes things all that much more
    fragile.  Recursion isn't as big a deal as linking.  Linked partition
    tables are a disaster waiting to happen.  No thanks!

					Matthew Dillon 
					<dillon at backplane.com>

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