My last post close to this topic gave me more information I could imagine in
my wildest dreams. (About humans & electric conducting as well!)Thank you
everyone.

I'm curious. Lets say you have two HD's on your linux box. The secondary you
use much as a backup medium. Then you want to replace the secondary drive
while computer is on.
If you spin down a hard disk is it OK to remove it and replace while power
is on? I suppose not, but please speculate and analyze the events of hotswap
ordinary IDE disk. Would it make difference if the disk is on mobilerack or
not?
Professional electricians are welcome to join this conversation and give
your opinions!

Mr.Jason
-----
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Mr.Jason wrote:

> If you spin down a hard disk is it OK to remove it and replace while power
> is on? I suppose not, but please speculate and analyze the events of
> hotswap ordinary IDE disk. Would it make difference if the disk is on
> mobilerack or not?

theoretically there would be little risk to the drive, however let's note
that for an IDE setup, the connector goes to the motherboard and no
motherboard I know of is designed to allow hot swapping of IDE cables.
There are risks to such a strategy, and I note that drive manufacturers all
insist that power be removed by turning off the computer before removing a
drive or installing one.

For drives in situations designed for hot swapping ala firewire and USB, the
risk is a lot less, in fact if you want to swap drives, one of those two
choices is a much better choice, just remember to unmount the drives before
removing them, the OS works a lot better not looking for a now non-existent
drive.

Art Clemons wrote:
> For drives in situations designed for hot swapping ala firewire and USB, the
> risk is a lot less, in fact if you want to swap drives, one of those two
> choices is a much better choice, just remember to unmount the drives before
> removing them, the OS works a lot better not looking for a now non-existent
> drive.

Note that there are converters available, which provide kind of an
overhead for IDE, so you can connect your IDE disk via USB, thus making
its removal safer.

~Mik

--
Macht ruhig weiter. Die Zeit, oder ein weniger gnädiger Faktor
natürlicher Auslese, werden auch eurer, wie damals meiner, Arä ein Ende
bereiten.

On Wed, 01 Jun 2005 16:06:16 +0300, Mr.Jason wrote:

> If you spin down a hard disk is it OK to remove it and replace while power
> is on?

How do you "spin down" a HD while power is on?

> I suppose not, but please speculate and analyze the events of
> hotswap ordinary IDE disk.

It would likely destroy the motherboard, and maybe the HD.

> Professional electricians are welcome to join this conversation and give
> your opinions!

This question is just as stupid as your other one about PCI cards. My
opinion is that you are an idiot.

> Mr.Jason
> -----

Learn how to properly use a signature block delimiter.

--
If you're not on the edge, you're taking up too much space.
Linux Registered User #327951

> Note that there are converters available, which provide kind of an
> overhead for IDE, so you can connect your IDE disk via USB, thus making
> its removal safer.
>
> ~Mik
>
> --
> Macht ruhig weiter. Die Zeit, oder ein weniger gnädiger Faktor natürlicher
> Auslese, werden auch eurer, wie damals meiner, Arä ein Ende bereiten.

Thanks! This sounds like an option to me.
Mr.Jason

> How do you "spin down" a HD while power is on?

I thought this was one of the things that professionals know
I suppose I was wrong, or then you are not professional

hdparm -y /dev/hdb

>> I suppose not, but please speculate and analyze the events of
>> hotswap ordinary IDE disk.
>
> It would likely destroy the motherboard, and maybe the HD.

How would it? can you answer for that? What parts of the motherboard?

>
>> Professional electricians are welcome to join this conversation and give
>> your opinions!
>
> This question is just as stupid as your other one about PCI cards. My
> opinion is that you are an idiot.

OK, its your opinion and then?

On Wed, 01 Jun 2005 17:38:27 +0300, Mr.Jason wrote:

>> How do you "spin down" a HD while power is on?

> hdparm -y /dev/hdb

You probably want the "-Y" flag instead. And just to err on the save side,
either "sync" or "hdparm -f /dev/hdb" (and mark it failed in raidtab
ofcource) before yanking it out.

>> It would likely destroy the motherboard, and maybe the HD.
>
> How would it? can you answer for that? What parts of the motherboard?

I suppose if your disks don't physically sit in a swapable bracket, you
could conceivably fry your mobo by hitting a hot wire to some joint ...

--
-Menno.

On Wed, 1 Jun 2005 16:06:16 +0300, Mr.Jason Cried: Read These Runes!:
>
> I'm curious. Lets say you have two HD's on your linux box. The secondary you
> use much as a backup medium. Then you want to replace the secondary drive
> while computer is on.

I'd advise getting a bay designed specifically for hot swapping. I have
one, cost about $20.00 IIRC. You refer to a mobile rack below, if it is
what I think it is, it should work.

> If you spin down a hard disk is it OK to remove it and replace while power
> is on? I suppose not, but please speculate and analyze the events of hotswap
> ordinary IDE disk. Would it make difference if the disk is on mobilerack or
> not?

If you use a 2.4.xx kernel you can use hdparm -b0 to turn the buss off, turn
off power to the tray, and remove the drive. Note the drive must be
installed during boot or it's a no go threafter. (/proc/ide etc.)

The tray fits in a CD player sized slot.

Hdparm is not yet available for 2.6 kernels.

> Professional electricians are welcome to join this conversation and give
> your opinions!

Not hardly a pro but I've been doing this for a couple of years and haven't
fried anything yet (crosses fingers).

Thorn
--
Children seldom misquote you. In fact, they usually repeat word for
word what you shouldn't have said.

On Wed, 01 Jun 2005 17:07:13 +0200, Menno Duursma wrote:
> On Wed, 01 Jun 2005 17:38:27 +0300, Mr.Jason wrote:

> I suppose if your disks don't physically sit in a swapable bracket, you

's/swapable bracket/swappable caddy/'

And BTW, the NIC swapping thing i have pulled before too (for fun, not a
production box or anything) no-problemo. Just ifconfig down the interface,
rmmod the kernel module, and yank it out (strait.) Insert 'new' card,
modprobe the driver and ifconfig it up. Trying that with an Ensoniq sound
cart the kernel Panic'd (or Oops'd don't remenber) though. :-)

Kids, don't try this at home, if you actually give a damn about the
hardware you're pulling this with.

And if you want to play with junk HW: at least use a grounded wall outlet.

--
-Menno.

Mr.Jason wrote:

> My last post close to this topic gave me more information I could imagine
> in
> my wildest dreams. (About humans & electric conducting as well!)Thank you
> everyone.
>
> I'm curious. Lets say you have two HD's on your linux box. The secondary
> you
> use much as a backup medium. Then you want to replace the secondary drive
> while computer is on.
> If you spin down a hard disk is it OK to remove it and replace while power
> is on? I suppose not, but please speculate and analyze the events of
> hotswap ordinary IDE disk. Would it make difference if the disk is on
> mobilerack or not?
> Professional electricians are welcome to join this conversation and give
> your opinions!
>

You asked for it :^)

The typical failure mode for hot-plugging digital devices
is latch-up. The CMOS technology used to drive the pins on
a chip creates a structure similar to a thyristor (SCR).

If current above a certain (very small) limit is injected
into a pin *before* power is applied to the chip, latch-up
occurs. Both drive transistors switch on, shorting the
chip's power rails.

When supply power is applied, the transistors blow, letting
out the magic smoke.

Devices which are specifically designed for hot-plug, either
use chips which avoid latch-up by design or make sure that
power is connected before any other signals. Have a look at
an USB or CompactFlash connector. The power pins are mechanically
different and connect first.

Specifically, IDE hard drives have separate power supply
connectors. If you want to risk it, it's probably best to
hot plug the data cable while the disk is powered up.

Some trays allow hot plugging, others don't.

Get an USB2 enclosure for your disk. Much safer.

Kind regards,

Iwo