[101860] in RedHat Linux List
Re: diskcopy for linux
daemon@ATHENA.MIT.EDU (Jan Carlson)
Mon Nov 30 01:50:33 1998
Date: Mon, 30 Nov 1998 01:47:22 -0500
From: Jan Carlson <janc@iname.com>
To: dfox@belvdere.vip.best.com, RedHat Mailing List <redhat-list@redhat.com>
Resent-From: redhat-list@redhat.com
Reply-To: redhat-list@redhat.com
"David E. Fox" wrote:
> > Note that the 18432 used as the value of 'bs' is not critical, it could be
> > almost anything, bigger is generally better. Best is if it is a whole-
> > number multiple of the diskette track size (for 3.5HDdrives 18 sectors *
>
> I haven't played that much with bs= values in dd, at least on Linux.
> One thing I did notice early on when first using Linux is that having
> a bs= value wasn't all that crucial, at least in comparison with
> early versions of BSD (precursors to FreeBSD) I used previously. On
> those, having a bs= value was absolutely necessary; otherwise, the
> system would read a sector, write a sector, read a sector, write
> a sector, and generally run *very* slowly. Just upping that to 10K or
> so made an incredible difference back then.
>
> I suspect it has something to do with buffering - afaik linux reserves
> a whole disk track someplace in the kernel data (floppy track buffer) so
> perhaps having a bs= is superfluous, at least when dealing with
> floppies.
Another way to do it is
cp /dev/fd0 /tmp/x
(insert new diskette)
cp /tmp/x /dev/fd0
You will notice the second cp returns
in about 2 seconds, but the floppy drive light
stays on for about a minute. It is buffering
the entire disk, not just a track or sector.
>
>
> > Fred
> ------------------------------------------------------------------------
> David E. Fox Tax Thanks for letting me
> dfox@belvdere.vip.best.com the change magnetic patterns
> root@belvedere.sbay.org churches on your hard disk.
> -----------------------------------------------------------------------
>
> --
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--
Jan Carlson
janc@iname.com Scarborough, Ontario, Canada
Mailed with Netscape 4.5 on Red Hat Linux 5.2
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