Re: 'Semi-Hot-Swap' of IDE discs
<quote who="Alexander Steinert">
> Dear list,
>
> for backup purposes (on i386 architecture) I'm planning the purchase of
> two 60GB-IDE discs, an exchange frame [right word?] and a
> PCI-IDE-Controller Card. SCSI is no option due to the huge difference in
> the price, at least here in Germany.
>
> Since my knowledge about IDE/ATA is near zero I'm curious if it is
> possible to swap IDE disks without shutting down the PC. Of course most
> of the time and especially on exchange the disc will not be mounted.
>
> I know that there are (expensive) exchange frames made for this purpose,
> but is this the only way? Do you know controller cards which can handle
> this? What about a self-installed switch to turn the disc off before
> swapping?
It is possible, but it is dangerous, you run a high risk of
severe damage to the hardware. first you'll need some kind of controller
that supports hot swap. off the top of my head would be 3ware. sadly
they discontinued their 6800 series produces and i've read on this
list that the newer ones were worse(!) then the 6800 ..so you may want
to try to find another card. maybe the promise ata raid card can do hot
swap.
second if you don't fork out the cash for a ide hot swap backplane your
best bet I think would be to get a good removable disk drive holder,
and before removing the disk, power it down using hdparm. be sure nothing
is using the disk(no mounted filesystems etc). and you can possibly
remove it and replace it with another drive of the EXACT same type(same
model, same size, same cylinders, same heads etc), and power the drive up.
A word of warning though, on one of my systems with a Promise ATA/100(non
hot swap/raid) I plugged in a drive into a removable bay(actually it was
already there, just not in 'all the way'. the OS was booted(linux), but
the drive wasn't detected. so I pressed on the removable bay to see if
it was loose, *BANG* instant hard reboot.
I would never try this, but I suppose it is possible. I would not remove
a disk and leave the controller disk-less for longer then a few seconds.
have the other drive ready to go in immediately.
But i can tell you this, with my experience with 3ware raid cards,
which du support hot swap, I have had(several times) a drive failure
(in a 6-disk RAID-10 array) take down the entire system. Even though
it is hardware raid, and the data on that drive is mirrored to another,
it still can crash the system. today i had one such event, my co worker
and i tried to initiate a rebuild of the array and the controller just
flipped out, eventually dropping out of detection of the system. the
vendor tools could no longer detect the card or the drives, when
we tried to reboot it immediately kernel paniced when it tried to
unmount the array.
in short it depends how much risk you want to take. if you really need
hot swap, you gotta go with SCSI/SCA. you can do IDE hot swap in
some condititions but its not nearly as solid. I would reccomend just
doing cold swap. you could also try the IDE-> SCSI adapters they
may provide better hot-swap ability. or IDE-> firewire, or IDE->Fiber
channel(is there such a beast?)
nate
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