"Switch Out" Physical HDD (hard disk drive)

Hi,

I have a NEC desktop computer (1999) with Win98se.
This has two physical HDDs (my modification), an internal
"Master" HDD and a removable drawer for a "Slave" HDD. Note:
I couldn't get this two HDD system to "work" using CS (cable select).

I would like to add a 2 pole switch in the wires that supply power
to the internal HDD so I can "switch out" the internal HDD (make it
"disappear") when I want to put a "Master" drive in the drawer.

Will this "work"? If not, do you know of another method?

Thank You in advance, John

wrote in
:

I have a NEC desktop computer (1999) with Win98se.
This has two physical HDDs (my modification), an internal
"Master" HDD and a removable drawer for a "Slave" HDD. Note:
I couldn't get this two HDD system to "work" using CS (cable select).


Never rely on Cable Select, there are too many discrepancies in its use.
Always specify master and slave directly. (On the 80-wire cables, that means
also get the position right, master at far end of the line.)

I would like to add a 2 pole switch in the wires that supply power
to the internal HDD so I can "switch out" the internal HDD (make it
"disappear") when I want to put a "Master" drive in the drawer.

Will this "work"? If not, do you know of another method?


That won't work for ATA devices because the disk controller feeds info to the
BIOS at boot time. Maybe if both disks were fully connected at that time,
switching out later can work, but it's a very risky move. Removable drive
trays allow this, and if you're TOTALLY sure that the drives are identical
down to the fine details of partitioning, you may be able to hot-swap them,
but even then the risk of data loss is severe.

If you want to hot-swap disks, get them onto FireWire, USB, or some other
buss that supports this.

wrote in
:

I would like to add a 2 pole switch in the wires that supply power
to the internal HDD so I can "switch out" the internal HDD (make it
"disappear") when I want to put a "Master" drive in the drawer.


I use a couple of drive trays in my main system, and standardised the choices
I made between two other machines as well. Basically, always use master for
the internal disk, and slave for the trays. That way you get an easier time
swapping disks full of video between machines, etc. Ideally use one big
extended DOS partition and no primaries on those slave disks. I also have an
internal optical disk writer as master on the second IDE buss. This helps
with getting the best results from that and the internal disk during
intensive copy operations, etc. I used to try other ideas, but this scheme
results in the least conflict, and the best speed.

Lostgallifreyan wrote in
:

I also have an
internal optical disk writer as master on the second IDE buss.

Small extra point about that... If you ever want to experiment with 'live'
operating system CD's or DVD's, this is the way to go because they almost
certainly expect to boot from the master of the muss, not the slave.

I forget several other reasons, but I found that using the master of the
second buss for optical writers was generally far better than using the slave
position on either buss. (But switch off 'auto-insert notification' using the
OS system property config pages, because that way no intensive reads, or
auto-runs, happen. Better to only have that stuff happen when directly
requested (or refreshed by F5 key) by you.)

In message ,
writes:
Hi,

I have a NEC desktop computer (1999) with Win98se.
This has two physical HDDs (my modification), an internal
"Master" HDD and a removable drawer for a "Slave" HDD. Note:
I couldn't get this two HDD system to "work" using CS (cable select).

I would like to add a 2 pole switch in the wires that supply power
to the internal HDD so I can "switch out" the internal HDD (make it
"disappear") when I want to put a "Master" drive in the drawer.

Will this "work"? If not, do you know of another method?

Thank You in advance, John


If you're thinking of hot-swapping (or in this case hot-switching), I
think it won't (unless the two are _very_ identical), because the BIOS
reads the details of what's connected at boot. Also, the processor -
which is implementing the OS - will think it is reading, or worse
writing, to a certain place on the disc, and then suddenly will be
connected to a different disc.

If you're only going to operate your switch when the power is off, then
I can't see why it shouldn't work. And you wouldn't really need a 2 pole
switch, though most switches available to the hobbyist are two pole
anyway; just switching the red line ought to suffice, I think. Both is
probably safer, though.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf

The love that dared not speak its name, has become the love that won't shut
up. - Simon Fanshawe (article on Gay Comedy), Radio Times 25 Sept-1 Oct 2010

On Thu, 14 Jun 2012 13:06:56 -0400, put finger
to keyboard and composed:


I would like to add a 2 pole switch in the wires that supply power
to the internal HDD so I can "switch out" the internal HDD (make it
"disappear") when I want to put a "Master" drive in the drawer.

I can't see why that shouldn't work. However, you might like to run
the jumper pins through a switch so that you could program the
internal drive as either master or slave. That way both drives would
be visible to the OS.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

J. P. Gilliver (John) wrote:
In message ,
writes:
Hi,

I have a NEC desktop computer (1999) with Win98se.
This has two physical HDDs (my modification), an internal
"Master" HDD and a removable drawer for a "Slave" HDD. Note:
I couldn't get this two HDD system to "work" using CS (cable select).

I would like to add a 2 pole switch in the wires that supply power
to the internal HDD so I can "switch out" the internal HDD (make it
"disappear") when I want to put a "Master" drive in the drawer.

Will this "work"? If not, do you know of another method?

Thank You in advance, John


If you're thinking of hot-swapping (or in this case hot-switching), I
think it won't (unless the two are _very_ identical), because the BIOS
reads the details of what's connected at boot. Also, the processor -
which is implementing the OS - will think it is reading, or worse
writing, to a certain place on the disc, and then suddenly will be
connected to a different disc.

If you're only going to operate your switch when the power is off, then
I can't see why it shouldn't work. And you wouldn't really need a 2 pole
switch, though most switches available to the hobbyist are two pole
anyway; just switching the red line ought to suffice, I think. Both is
probably safer, though.

I'd second that. I sure wouldn't try it (switching it when the power is on).
I don't mind taking some risks, but I think that is a big one, for all the
reasons stated.

"J. P. Gilliver (John)" wrote in
:

Also, the processor -
which is implementing the OS - will think it is reading, or worse
writing, to a certain place on the disc, and then suddenly will be
connected to a different disc.


Actually the disk controller should keep track of that on its own disk, the
OS won't see that stuff personally, but there's still plenty to go wrong, not
least the cache...

"J. P. Gilliver (John)" wrote in
:

If you're only going to operate your switch when the power is off, then
I can't see why it shouldn't work. And you wouldn't really need a 2 pole
switch, though most switches available to the hobbyist are two pole
anyway; just switching the red line ought to suffice, I think. Both is
probably safer, though.


I didn't think that through before, but now I am, and I'd avoid it/ Maybe two
poles, one for 12V, one for 5V, but I'd leave the ground commoned at all
times, otherwise you might get momentary flows from one supply line to the
other, and I wouldn't be placing any bets on outcomes. Never mind harmful or
not, undefined behaviour is code's greatest enemy, so avoid it...

"Bill in Co" wrote in
m:

I'd second that. I sure wouldn't try it (switching it when the power is
on). I don't mind taking some risks, but I think that is a big one, for
all the reasons stated.


I think my drive trays let me stop the power when I turn the key. I never
eplored this much because of the risk, but what I do know: The drive powers
down, and will wake safely after restoring locked state, so long as the disk
was booted properly to start with. What I don't know: if data is lost when
doing this after a write due to a non-purged cache... I think I tried a read-
only swap after boot once to see what happened. If I remember right, not a
lot did. I think it might as well have been a 3.5 inch wide brick. I had to
put the original one back, and I rebooted anyway just to be safe.