Re: disk hot-swap utilities
On 11 Nov 2000 12:31:13 +0100, Ramin Motakef <ramin@motakef.de> wrote:
>
> "Noah L. Meyerhans" <frodo@morgul.net> writes:
>
> > I recently had the opportunity to use a FreeBSD feature that I found
> > extremely cool. I had built a machine, set it up as a server, deployed
> > the server, then realized I needed to add a disk. The machine and OS
> > support hot-swapping SCSI disks, so I was able to add a whole new disk,
> > previously 100% unknown to the system, without ever rebooting. The tool
> > to control the SCSI bus is called camcontrol on FreeBSD. My question
> > is, how is this done in Linux and Debian? Is the functionality as
> > mature and good?
> >
> > noah
> > --
> I never haf the opportunity to work at a hot swap system, but this is
> what works for my external SCSI CDRW Drive:
> 1) sync all disks
> 2) take away external terminate an
> 3) plug in the CDRW (fast!)
> 4) Turn Power of CDRW on
> 5) echo "scsi add-single-device 0 0 5 0" >/proc/scsi/scsi
> / \____
> /Host Channel ID LUN\
> 6) Done
>
> Read about it in /path/to/kernel-src/drivers/scsi/scsi.c
>
> Note:
> It is not possible to hot-plug a disk in a normal PC, as you will
> likely get a reset when you plug in the power connector of the disk
> (draws quite a lot of current when spinning up, [i tried it....]).
>
>
> After all, i would say it is possible, baut mature and good????
>
It's probably more adequate for external devices!
I've been using scsiadd on my Powerbook, which is available from
http://llg.cubic.org/misc/
and so far working like a charm. It probably does the above entry to
proc, and possibly a few more things (it checks IDs, so it won't
add an entry at a lower ID, e.g. if you already have /dev/sda, it
will only add disks with higher SCSI ID that become /dev/sdb etc.).
I can simply connect a device while the PB is sleeping, then turn on
the drive, wake up the PB and add the device and mount the disk
(this behaviour is supported in MacOS as well). I don't know how
well it will work on PCs, or on desktop machines in general (well
I did experiment with connecting external disk and tape drives to
my old Mac sometimes, which seemed to increase the likelyhood of
crashing).
Of course the usually disclaimer applies: SCSI is not meant for
hot-swapping, and I'll not be held responsible for anything that
happens when trying it -- but if the hardware says it supports
it, why not try it ;-).
Cheers,
Derek
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