At 14:58 Uhr -0400 05.07.2000, Robert wrote:
>1. If a drive is not present when the machine is booted, but is inserted
>after the machine is up, it can't be mounted. (You get a message that the
>device is not a valid block device.)
You must tell the Kernel about this new device. This is also mentioned in the
RAID-Howto:
echo "scsi add-single-device a b c d" > /proc/scsi/scsi
a (controller) b (cannel) c (id) d (lun)
you may also unregister devices via
echo "scsi remove-single-device a b c d" > /proc/scsi/scsi
Sometimes hot-plugging won't work as expected (have seen this occassionally). What I'd
love to see would be
echo "scsi reset-single-device a b c d" > /proc/scsi/scsi
to to a device reset with resetting the (must be) following unit attention or a bus
reset if the id matches the id of the hostadapter.
I think the LUN could be safely ignored in both cases.
echo "scsi reinit a b" > /proc/scsi/scsi would be also nice but I am not sure if this
could be safely implemented (without losing data on the particular
controller/channel). I had the problem that an Adaptec 2940AU tried to BUS RESET a bus
with no actual members (after trying to hot plug somthing onto it) for about 2 hours
before add-single-device finally timed out...
Unfortunately I have no clue to whom I may tell this to perhaps get this implemented.
:-)
>2. If a drive is present at boot time, and then later removed and then
>later yet re-inserted, it cannot be mounted. This occurs even if the
>drive was never accessed before re-inserting. (You get scsi disk error
>messages.)
This heavily depends on the SCSI hardware implementation.
On single ended buses this is usually not a big problem to to (altough it is wise to
remove-single device the dis prior to removing). UW-Buses usually get stuck and work
fine after a BUS RESET. I have no real tests done with LVD at this time.
>Is there some step I am missing? If not, I do not think "hot-swap" drives
>work very well with linux, since any change in the disks requires
>rebooting. Granted I did not have to power the machine off/on, but I do
>seem to have to reboot. Perhaps I am just miss-understanding the meaning
>of "hot-swap".
Hot-Swap is divided into hard- and software. You simply missed the software part :-)
:wq! PoC
