SATA and Hot Swap (More info)

I found this discussion very interesting as I am wanting to be able to
hot swap some drives myself. What is the symptom when one swaps a drive
in or out that is not "hot swap capable"? Is the drive merely not
recognized, or can hardware damage occur?
Thanks,
--
Charlie C.
To email me, eradicate obfuscate & remove dot invalid

CSquared wrote:
I found this discussion very interesting as I am wanting to be able to
hot swap some drives myself. What is the symptom when one swaps a drive
in or out that is not "hot swap capable"? Is the drive merely not
recognized, or can hardware damage occur?
Thanks,
--
Charlie C.
To email me, eradicate obfuscate & remove dot invalid


It sounds like Carl has done more experiments with this
than I have.

If the hot swap is not working, then you wouldn't expect
the system to see the disk at all. The event from the
hardware, would not be raised to the software (because
either the path is missing inside the driver code, or
the OS itself doesn't support drives appearing out of
nowhere).

The SATA connectors are designed with hot swap in mind,
and even if the driver code was missing, there should be
no damage to the drive. If you look at the SATA cable,
certain pins are longer than the other pins. Those pins
touch first, and prevent negative voltages appearing on
the sensitive data pins.

If you look at the instructions for one of those
SATA to USB converters, they suggest a certain order
if connecting cables to a cold drive. Connect the 15 pin
SATA power wafer first. Then connect the data cable second.
When you think about it, you should be connecting your
cables, to minimize vibration to a running drive, so one
end of the data cable can be fastened to the drive first,
then the power cable gets connected, and then the other
end of the data cable goes to the motherboard.

When you're finished with the drive later, and you want
the OS to keep running, first you use the "Safely remove"
icon in the tray, to flush the cache on the drive. Then,
you'd unplug the data cable from the motherboard connector.
(That way, there is no mechanical shock to the still-powered
drive.) Next, disconnect the power to the drive, preferably
by disconnecting an adapter cable from the power supply - not
by yanking on a connector right on the drive. So when you're
finished, you have a drive in your hands, with a power and
a data cable still in place, but the other ends have been
disconnected in a particular order. Once the drive spins
down (give it 30 seconds or more), it is more resistance
to shock, so you can carefully remove the cables from the
drive.

It is sorta like car batteries, when you give you buddy's car
a boost. There is a certain order to connect the cables
there as well, for safety reasons.

HTH,
Paul

"Paul" wrote in message
...
CSquared wrote:
I found this discussion very interesting as I am wanting to be able
to
hot swap some drives myself. What is the symptom when one swaps a
drive
in or out that is not "hot swap capable"? Is the drive merely not
recognized, or can hardware damage occur?
Thanks,
--
Charlie C.
To email me, eradicate obfuscate & remove dot invalid


It sounds like Carl has done more experiments with this
than I have.

If the hot swap is not working, then you wouldn't expect
the system to see the disk at all. The event from the
hardware, would not be raised to the software (because
either the path is missing inside the driver code, or
the OS itself doesn't support drives appearing out of
nowhere).

The SATA connectors are designed with hot swap in mind,
and even if the driver code was missing, there should be
no damage to the drive. If you look at the SATA cable,
certain pins are longer than the other pins. Those pins
touch first, and prevent negative voltages appearing on
the sensitive data pins.

Both of the above paragraphs are pretty much what I would have expected.
I really had not done my homework on this issue and probably should not
have posted regarding it at all yet, but I figured what the heck - it
was the first work day of the new year. Also, it is a subject in
which I have more than passing interest.


If you look at the instructions for one of those
SATA to USB converters, they suggest a certain order
if connecting cables to a cold drive. Connect the 15 pin
SATA power wafer first. Then connect the data cable second.
When you think about it, you should be connecting your
cables, to minimize vibration to a running drive, so one
end of the data cable can be fastened to the drive first,
then the power cable gets connected, and then the other
end of the data cable goes to the motherboard.

When you're finished with the drive later, and you want
the OS to keep running, first you use the "Safely remove"
icon in the tray, to flush the cache on the drive. Then,
you'd unplug the data cable from the motherboard connector.
(That way, there is no mechanical shock to the still-powered
drive.) Next, disconnect the power to the drive, preferably
by disconnecting an adapter cable from the power supply - not
by yanking on a connector right on the drive. So when you're
finished, you have a drive in your hands, with a power and
a data cable still in place, but the other ends have been
disconnected in a particular order. Once the drive spins
down (give it 30 seconds or more), it is more resistance
to shock, so you can carefully remove the cables from the
drive.

It is sorta like car batteries, when you give you buddy's car
a boost. There is a certain order to connect the cables
there as well, for safety reasons.

That makes perfect sense to me. My current vision for using a removable
drive is primarily as a mostly-non-spinning alternate backup for .jpg
files I've saved from my camera. (I'm a firm believer in multiple -
like 3 or more - backups for irreplaceable things like digital pictures.
And yes, I have multiple CDs burned at intervals, but I'd still like to
have them on a different medium as well.) In that scenario, I would
probably just leave the power and data cables connected to the external
drive essentially all the time. I can just hear someone say "Yeah, but
what happens when you fill that drive up and need 2 or more drives?"
I'll grant everyone ahead of time that is a real possibility. I suppose
an extra set of cables for each external drive would not add all that
much more cost though.

I was actually thinking more in terms of the hot-swap trays one can
mount in a drive bay, since I always tend to over-build in the area of
the PC case and have lots of spare empty drive bays as a result. I did
today finally do a bit of homework and found quite a few of these at my
favorite internet vendor (Newegg - no affiliation, just a happy
customer) in the $25 to $35 US range. Several mention being
"master/slave free" which I'll admit I had not thought about.

In any case, thanks much for your comments.
Charlie C.


HTH,
Paul