Hello Ian,
* Ian M. Moore ([EMAIL PROTECTED]) [990422 07:50]:
> Soon I will be given the opportunity to install linux on a Dell Poweredge
> 2300.(vacuum cleaner )
> The only problem I see right now is it has scsi hotswapable harddrives.
> Has anyone installed linux on such a machine?
> Any info much appreciated.
> Thanks,
> Ian
Well, the Hotswapping SCSI hard drives can't be a problem if you don't
swap them. :-)
More seriously, hot swapping is a bit of a complicated topic.
Some SCSI chassis are set up with external drive bays with integrated
connectors on the back so drives can be added or removed with one action.
These are not necessarily hot swappable at all, although some manage to
get away with doing so (hey.. some people overclock their processors too,
and it even works sometimes.) In this sort of a system there is _no_
guarantee that the SCSI bus will maintain integrity when attaching or
detaching components. You could concievably harm SCSI components doing
this, as well as loose data on the bus.
Some SCSI systems you have proper attachment and detachment connectors
with will maintain the bus' electrical properties and allow SCSI devices
to come and go without corrupting signals on the bus. However, the SCSI
controller (in hardware, firmware, or both), SCSI driver, and opreating
system must all be equipped to handle the removal and addition of SCSI
devices. This sort of thing is less frequently done than many other SCSI
configurations, so problems can exist at any of the three areas I
mentioned. Nowhere in my brief reading was there any sort of statement
that claimed the ability of the Linux SCSI subsystem was very robust and
well tested in this sort of situation, but many posters seemed comfortable
doing so. A bash script to force a SCSI bus rescan was posted in a
discussion an ncr mailing list archived here:
http://linuxwww.db.erau.edu/mail_archives/ncr/Oct_98/
The script in question was attached to this message:
http://linuxwww.db.erau.edu/mail_archives/ncr/Oct_98/0010.html
You might well want to skim through the SCSI Programming HOWTO:
http://metalab.unc.edu/mdw/HOWTO/SCSI-Programming-HOWTO.html
or zless /usr/doc/howto/en/SCSI-Programming-HOWTO.gz
This is also touched on by a page on RAID Solutions for Linux
Hot-Plug Support
Linux supports "hot-plug" SCSI in the sense that SCSI devices can be
removed and added without rebooting the machine. The procedures for
this are documented in the SCSI Programming HOWTO. From the
command-line, the commands are
echo "scsi remove-single-device host channel ID LUN " > /proc/scsi/scsi
echo "scsi add-single-device host channel ID LUN " > /proc/scsi/scsi
Don't confuse this ability with the hot-plug support offered by
vendors of outboard raid boxes.
I also recommend looking into the documentation for and comments in your
particular SCSI controller's driver located in the directory
/usr/src/linux/Documentation/drivers/scsi/.
In any event, be sure to unmount your filesystems before you take the
disks off-line.
Meanwhile, if this is some sort of a hardware RAID system, this should all
be transparent to the operating system and require no special
configuration at all. These systems are very nice, but very expensive.
Best of luck,
-josh
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