Ok to leave slave HD cable connected with power off?

  • Thread starter Thread starter Mark
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Mark

I want to use a slave hard drive occasionally as a Drive Image backup disk.
I don't like the idea of the backup hard drive always being powered on
because hard drives are rated for a certain number of on/off cycles. Can I
just unplug the power cable and leave the flat ribbon cable connected when I
don't need to use the backup drive or will that create some reliability
issues with my master hard drive on the end of the cable?
 
A neater solution would be a removeable HDD caddy - about £15 - fits into 5
1/4" bay and the HDD caddy slides in and out. You can't hot-swap ofcourse,
but when you wanted to access the drive you've only got to slide it in
before booting.
Will not cause any probs for your bootdrive.
 
Mark said:
I want to use a slave hard drive occasionally as a Drive Image
backup disk. I don't like the idea of the backup hard drive
always being powered on because hard drives are rated for
a certain number of on/off cycles. Can I just unplug the power
cable and leave the flat ribbon cable connected when I don't
need to use the backup drive or will that create some reliability
issues with my master hard drive on the end of the cable?
Click to expand...


This has been discussed several times in the past year, and
although there are the usual specification freaks, no one had
any verifiable reason or data to indicate that having a "dead"
HD at the intermediate position of an IDE cable would hurt
the data in any way. I can't think of an obvious reason not
to have the "dead" HD at the *end* of the cable, either, since
I can't see why the "dead" circuitry (i.e. unpowered circuitry)
at the end of the cable would cause less or more signal
reflections than "live" circuitry.

The question does arise, though, why you can't unplug
the intermediate connector from the HD as well as the
power connector? Are you planning on controling the
HD power with a switch? If so, make that switch hard
to reach! :-)

*TimDaniels*
 
Timothy said:
This has been discussed several times in the past year, and
although there are the usual specification freaks, no one had
any verifiable reason or data to indicate that having a "dead"
HD at the intermediate position of an IDE cable would hurt
the data in any way. I can't think of an obvious reason not
to have the "dead" HD at the *end* of the cable, either, since
I can't see why the "dead" circuitry (i.e. unpowered circuitry)
at the end of the cable would cause less or more signal
reflections than "live" circuitry.
Click to expand...

What about potential harm to the unpowered drive's interface
circuits?
 
GTS said:
A neater solution would be a removeable HDD caddy - about £15 - fits into 5
1/4" bay and the HDD caddy slides in and out. You can't hot-swap ofcourse,
but when you wanted to access the drive you've only got to slide it in
before booting.
Click to expand...

Before power-on actually.
 
Timothy Daniels said:
This has been discussed several times in the past year, and
although there are the usual specification freaks, no one had
any verifiable reason or data to indicate that having a "dead"
HD at the intermediate position of an IDE cable would hurt
the data in any way.
Click to expand...

Of course it will not proactively do anything since it's powered-off.
I can't think of an obvious reason not
to have the "dead" HD at the *end* of the cable, either, since
I can't see why the "dead" circuitry (i.e. unpowered circuitry)
at the end of the cable would cause less or more signal
reflections than "live" circuitry.
Click to expand...

Middle of the cable, as what's being discussed is a slave drive. The
question is will unpowered circuitry behave well on an active/powered cable.
Will it load something or draw current...I don't know.
 
Ron Reaugh said:
Of course it will not proactively do anything since it's powered-off.


Middle of the cable, as what's being discussed is a slave drive. The
question is will unpowered circuitry behave well on an active/powered cable.
Will it load something or draw current...I don't know.
Click to expand...


The question is whether data on its way to the end connector would
be absorbed or reflected in some way by the dead circuitry at the
intermediate position. I've tried it. The answer is that the data on
its way to the end connector is not corrupted.

*TimDaniels*
 
"CJT" asked:
What about potential harm to the unpowered drive's interface
circuits?
Click to expand...


Why should they be harmed when unpowered and not harmed
when powered?

*TimDaniels*
 
Timothy said:
Here's the answer: There's no harm. I've tried it.

*TimDaniels*
Click to expand...

Does the standard contain language requiring that they be designed to
not be harmed that way? Anecdotal evidence is just that -- it doesn't
necessarily carry over to drives on which it was not observed.
 
CJT said:
Does the standard contain language requiring that they
be designed to not be harmed that way? Anecdotal
evidence is just that -- it doesn't necessarily carry over
to drives on which it was not observed.
Click to expand...


The "standards" don't say anything about that situation
that I know of. Of more importance to me is that it's
a "don't care" for my hard drives (Maxtor DiamondMax
Plus 9s). You are free to care and to fear as much as
you desire. For others, it's an easy experiment.

*TimDaniels*
 
CJT said:
Who knows what state they're in when they're unpowered?
Click to expand...


1) Is there a "state" when the circuits are unpowered?
2) How is the "state" of an unpowered circuit going to
affect the signal passing by?
3) Why don't you try it and see?

*TimDaniels*
 
Timothy Daniels said:
This has been discussed several times in the past year, and
although there are the usual specification freaks, no one had
any verifiable reason or data to indicate that having a "dead"
HD at the intermediate position of an IDE cable would hurt
the data in any way. I can't think of an obvious reason not
to have the "dead" HD at the *end* of the cable, either, since
I can't see why the "dead" circuitry (i.e. unpowered circuitry)
at the end of the cable would cause less or more signal
reflections than "live" circuitry.

The question does arise, though, why you can't unplug
the intermediate connector from the HD as well as the
power connector? Are you planning on controling the
HD power with a switch? If so, make that switch hard
to reach! :-)
Click to expand...
No switch. I just don't want to wear out the connector/pins.
 
GTS said:
A neater solution would be a removeable HDD caddy - about £15 - fits into 5
1/4" bay and the HDD caddy slides in and out. You can't hot-swap ofcourse,
but when you wanted to access the drive you've only got to slide it in
before booting.
Will not cause any probs for your bootdrive.
Click to expand...
I have a StarTech removable drive caddy (DRW115ATA) already on the end of
the cable. After reading prior discussions on this group, I would be
worried about signal reflections caused by a removable caddy in the middle
of the cable and making the total cable length too long.
 
Timothy said:
1) Is there a "state" when the circuits are unpowered?
Click to expand...

Of course.
2) How is the "state" of an unpowered circuit going to
affect the signal passing by?
Click to expand...

Who knows unless it's specified by the designer?
3) Why don't you try it and see?
Click to expand...

Because it's an engineering question. Would you just build a
bridge and see if it stays up? If it stays up the first time
a car goes over it, is that good enough?
 
CJT said:
Of course.


Who knows unless it's specified by the designer?


Because it's an engineering question. Would you just build a
bridge and see if it stays up? If it stays up the first time
a car goes over it, is that good enough?
Click to expand...


Relax and live life, CJT. Not everything is specified.

*TimDaniels*
 
Mark said:
into
I have a StarTech removable drive caddy (DRW115ATA) already on the end of
the cable. After reading prior discussions on this group, I would be
worried about signal reflections caused by a removable caddy in the middle
of the cable and making the total cable length too long.
Click to expand...

The reflection issue appears more severly when there's nothing powered at
the end of the cable. The middle of the cable is much less important. The
design must include keeping the overall cable length in check.
 
Ron Reaugh said:
The reflection issue appears more severly when there's
nothing powered at the end of the cable.
Click to expand...

You are correct in that there should be a device
connected at the end of the cable to avoid the
reflections (and the timing of those reflections as
they reach the intermediate device), but of what
significance is there in the end device being
powered or not? Implicit in your statement is
the assumption that the impedance looking into
the device from the connector is different
according to whether it was powered or not.
Why should the input impedance change with
power?

*TimDaniels*
 
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