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'[OT]: PICList.com up after Hard Drive reformat'
2001\02\13@180011 by jamesnewton

face picon face
Its back up. But I don't like this kind of problem. I'm going to concentrate
on figuring out what I did wrong with the UPS to Server communication and
then try to get together some hard drives to get RAID going.

In a raid system, are standard drives "Hot Swappable"? I.e. can you just
pull the cover off the box, unplug the drive that failed and replace it and
then format the new drive and have NT replicate the data from the other two
drives back onto it?

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{Original Message removed}

2001\02\13@192325 by David VanHorn

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face
>
>In a raid system, are standard drives "Hot Swappable"? I.e. can you just
>pull the cover off the box, unplug the drive that failed and replace it
>and then format the new drive and have NT replicate the data from the other two
>drives back onto it?

They have to be SCSI to be hot swappable, and it has to be the right raid
level.

Me, I'd use linux. (Raid's built in too :)

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2001\02\13@195024 by Brandon, Tom

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picon face
To be replaceable without a shutdown you need a RAID\SCSI card that's
supports Hot swap (I think only RAID and REAL expensive SCSI would support
this), drives that support Hot swap and drive bays for hot swap. Here in
Australia, it was about AU$20 extra on an 18.2Gb SCSI to get Hot swap but
the drive bays were about AU$250 (about 1\2 the price of the drives but
SCSI's quite expensive here) each so overall it was quite expensive.

Using NT's software RAID: with a stripe set you need to manualy start
regeneration once the new drive is installed (this requires reboot). I'm not
sure but I have a feeling NT will disallow access when one member of a
stripe or mirror set is down. Maybe it'll allow reading but as you can't
write in a fault tolerant manner I doubt it will allow it. For unattended
recovery you would need hardware RAID with a hot spare drive, again unless
you had the hot spare drive fault tolerant writing is not possible so I
doubt writing would be allowed. Adaptec have a UDMA\66 RAID card that might
allow a cheap system with a hot spare drive to be constructed. This way, the
card would automatically add the spare drive to the set if one drive failed.
You'd have to shutdown the machine at some point to replace the faulty drive
but there would be no urgency. However I'm not 100% sure that UDMA RAID
cards support hot spares or on the fly regeneration.

Tom.
{Original Message removed}

2001\02\13@195923 by David VanHorn

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face
At 11:53 AM 2/14/01 +1100, Brandon, Tom wrote:
>To be replaceable without a shutdown you need a RAID\SCSI card that's
>supports Hot swap (I think only RAID and REAL expensive SCSI would support
>this), drives that support Hot swap and drive bays for hot swap. Here in
>Australia, it was about AU$20 extra on an 18.2Gb SCSI to get Hot swap but
>the drive bays were about AU$250 (about 1\2 the price of the drives but
>SCSI's quite expensive here) each so overall it was quite expensive.

All scsi devices and cards are hot-swap. SCSI is natively hot-swap.
There are caveats, like you have to be running raid, or make sure the drive
is dismounted.


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2001\02\13@202042 by Brandon, Tom

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You might like to have a chat with Adaptec about that:
<BLOCKQUOTE>
Q: Does the AHA-3950U2 support hot swap of SCSI devices?

A: No, not for devices directly connected on the SCSI cable. Hot swap is a
function of the device enclosure. Specific enclosure design is required to
ensure that power is removed from the SCSI device and the device isolated
from the bus before it is removed. Power surges or bus lockup will occur if
a device connected directly to a cable is removed or connected while the
system is functional.
</BLOCKQUOTE>

The "Hot swappable" drives I was referring to are SCA drives. SCA refers to
Single Connector Attach. From what I can tell, SCA means that the last
device on the bus will automatically terminate. Sorry, I'd had SCA described
as hot swappable by our supplier when they're not quite the same.

Tom.
{Original Message removed}

2001\02\13@204602 by David VanHorn

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face
At 12:23 PM 2/14/01 +1100, Brandon, Tom wrote:
>You might like to have a chat with Adaptec about that:
><BLOCKQUOTE>
>Q: Does the AHA-3950U2 support hot swap of SCSI devices?
>
>A: No, not for devices directly connected on the SCSI cable. Hot swap is a
>function of the device enclosure. Specific enclosure design is required to
>ensure that power is removed from the SCSI device and the device isolated
>from the bus before it is removed. Power surges or bus lockup will occur
>if a device connected directly to a cable is removed or connected while
>the system is functional.
></BLOCKQUOTE>

Well, I know that's their position.
However, properly implemented SCSI will not lock up, and will re-try any
trashed transaction. Been there, done that, wrote the code myself.
This is kind of like the W95 version of SCSI which didn't support LUNs.
Apparently MS didn't feel like implementing that part of the spec, so they
just tossed it out.

SCSI also supports multiple computers on the bus, but Adaptec's software
dosen't do that either.

In my view, an ANSI spec is not a "Chinese Menu". You either implement all
of it, or what you've done is "This wierd thing that we came up with
ourselves".



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2001\02\13@211815 by Randy Glenn

picon face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Actually, Promise Technology's SuperTrak card can do hot-swapping
with up to 6 IDE hard disks, with RAID 5. No Linux support, though.

- -Randy Glenn

This coming from the guy with a system tray 7 icons wide... by 2
tall...
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- {Original Message removed}

2001\02\13@221434 by Bob Ammerman

picon face
> However, properly implemented SCSI will not lock up, and will re-try any
> trashed transaction.

Yes, but without power sequencing and disconnection you risk _physical_
damage to any and all devices attached to the bus.

> Been there, done that, wrote the code myself.
> This is kind of like the W95 version of SCSI which didn't support LUNs.
> Apparently MS didn't feel like implementing that part of the spec, so they
> just tossed it out.

Of course the fact that almost nobody ever used LUNs (the only exception I
know of is an ancient Bournoulli box) might have something to do with it.

> SCSI also supports multiple computers on the bus, but Adaptec's software
> dosen't do that either.

Again, not some often used.

> In my view, an ANSI spec is not a "Chinese Menu". You either implement all
> of it, or what you've done is "This wierd thing that we came up with
> ourselves".

This is a good point.

>

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\13@221828 by Dale Botkin

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> In my view, an ANSI spec is not a "Chinese Menu". You either implement all
> of it, or what you've done is "This wierd thing that we came up with
> ourselves".

Along those lines, I heard a really good quote the other day.  I was
watching Scott McNealy from Sun address some press organization on C-Span.
Holding up a coffee cup to illustrate what Microsoft had done with Java, he
said something like: "Let's say I have this cup of Java.  Now I remove a
little bit of the Java and put in three drops of poison.  Now what do I have
in the cup?  Is it Java, or is it poison?" ..pause.. "Neither.  It's now
called Windows."

Chuckle...  Thought I'd choke on my coffee, I was laughing so hard.

Dale

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2001\02\13@222110 by Mitch Miller

picon face
That's not entirely true ... while the SCSI protocol may allow drives to
come and go, you still have to consider the electrical interface.  You can't
(practically speaking) just open your case and pull the cable from a drive.
Most hot-swapping drive bays connect the power (at least the GND) lead prior
to the signals.  I believe PCMCIA and CARDBUS cards do the same.

-- Mitch

{Original Message removed}

2001\02\13@222131 by Mitch Miller

picon face
I don't think, however, that the SCA connector implements power.  So ... you
still have to connect power ahead of the bus.

--Mitch

{Original Message removed}

2001\02\13@222751 by Robert Shady

picon face
Yes, they do.. That is their entire purpose.  The
support EVERYTHING on a single connector (most of
the time you don't need to set the id, or anything).

These drives are MADE for RAID.. And you pay for it.

-- Rob

--- Mitch Miller <.....mdmiller2KILLspamspam@spam@HOME.COM> wrote:
> I don't think, however, that the SCA connector implements power.  So
> ... you
> still have to connect power ahead of the bus.
>
> --Mitch
>
> {Original Message removed}

2001\02\13@230746 by Mitch Miller

picon face
> Of course the fact that almost nobody ever used LUNs (the only exception I
> know of is an ancient Bournoulli box) might have something to do with it.

The Panasonic PD/CD drive also used multiple LUNS as I recall.  One for the
CD "side" and one for the optical drive.

-- Mitch

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2001\02\13@230803 by Mitch Miller

picon face
I just implemented two Atlas 10k-II drives in a server (one 36 Gb, and one
72 Gb) and had to connect power to both of them.  As I recall, they had the
SCA connector on them.  Perhaps I've mistaken my TLAs (TLA = three letter
acronym) <g>.

-- Mitch

{Original Message removed}

2001\02\13@232623 by Dale Botkin

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face
> I just implemented two Atlas 10k-II drives in a server (one 36 Gb, and one
> 72 Gb) and had to connect power to both of them.  As I recall,
> they had the
> SCA connector on them.  Perhaps I've mistaken my TLAs (TLA = three letter
> acronym) <g>.

Probably.  SCA is an 80-pin connector that carries power, SCSI signals,
drive ID, everything on one conenctor.  They are only made as OEM devices,
to me knowledge no drive manufacturer sells them to consumers.  if you're
Sun, Dell, Compaq, IBM, etc and are buying a few thousand it's the way to
go.  Well, actually, if you're IBM you manufacture your own and sell to the
others.

You can get adapters to connect SCA drives to 50- or 68-pin SCSI narrow,
wide, Ultra, etc. controllers.  I paid $10 each for mine to connect SCA
drives to an old Adaptec 2940U narrow/ultra controller via 50-pin cable.
The adapter has a 50-pin SCSI connector, power conector, ID jumpers and a
terminator you can install or leave off, along with a few other normal SCSI
option jumpers.

Dale

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2001\02\13@234338 by Kevin Maciunas

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picon face
On Tue, 13 Feb 2001 22:19:54 -0600 Dale Botkin <Dale Botkin <dalespamKILLspamBOTKIN.ORG>> wrote:

pmdl> > I just implemented two Atlas 10k-II drives in a server (one 36 Gb, and one
pmdl> > 72 Gb) and had to connect power to both of them.  As I recall,
pmdl> > they had the
pmdl> > SCA connector on them.  Perhaps I've mistaken my TLAs (TLA = three letter
pmdl> > acronym) <g>.
pmdl> pmdl> Probably.  SCA is an 80-pin connector that carries power, SCSI signals,
pmdl> drive ID, everything on one conenctor.  They are only made as OEM devices,
pmdl> to me knowledge no drive manufacturer sells them to consumers.  if you're
pmdl> Sun, Dell, Compaq, IBM, etc and are buying a few thousand it's the way to
pmdl> go.  Well, actually, if you're IBM you manufacture your own and sell to the
pmdl> others.
pmdl> pmdl> You can get adapters to connect SCA drives to 50- or 68-pin SCSI narrow,
pmdl> wide, Ultra, etc. controllers.  I paid $10 each for mine to connect SCA
pmdl> drives to an old Adaptec 2940U narrow/ultra controller via 50-pin cable.
pmdl> The adapter has a 50-pin SCSI connector, power conector, ID jumpers and a
pmdl> terminator you can install or leave off, along with a few other normal SCSI
pmdl> option jumpers.
pmdl>
For what it's worth, some (perhaps all, but I've not seen *ALL*) SCA drives also
have a power supply connector on the drive (but not the "usual" PSU connector, I
hasten to add).  I didn't have any bother getting SCA drives from the local
suppliers - they didn't have them in stock, but got them direct from Seagate (as
I recall).  The only problem I've ever had with SCA format drives was in trying to source an
SCA connector to add another drive into a (now old) Sun SparcStation 4 - at the
time, no-one admitted to making them, even when you read out the P/N on the
connector :-)
/Kevin
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2001\02\14@004444 by mmucker

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face
Yes, SCSI is natively hot-swap, but NT4 won't re-enumerate the SCSI bus once
it's up. :(

Software based RAID just isn't appropriate for server solutions.

-Matt
>
> All scsi devices and cards are hot-swap. SCSI is natively hot-swap.
> There are caveats, like you have to be running raid, or make sure
> the drive
> is dismounted.
>

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2001\02\14@005249 by Bill Westfield

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   Of course the fact that almost nobody ever used LUNs (the only exception I
   know of is an ancient Bournoulli box) might have something to do with it.

I have a 7-disk CD changer with a separate LUN for each disk.  Best impulse
purchase I've ever made...  Had to patch freebsd to get it to work right
there, though.  W98 handles it fine by default, I think.

BillW

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2001\02\14@005311 by M. Adam Davis

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Whether a device is hot swappable depends on two or three things:
1) If the electrical connection can be broken without transient (or the
bus can recover from such a transient)
2) If the hardware interface can handle attaching and detaching devices,
recognizing them in real time
3) (depends on the setup) if the software can handle the attachment and
detachment.

This means you need a hot-swap enclosure or connector for the drive, a
controller that understands what's going on, and possibly an OS that
knows what's going on.

There are hot-swap for both SCSI and IDE drives, and many hardware RAID
cards handle it transparantly to the system.  The Promise FastTrack, for
instance, with hard drive hot-swap bays in a mirror or mirror/stripe
configuration will allow you to take a drive out of the system while
running, replace it, and the FastTrack will rebuild the data on the new
drive from the current drives.  All this _can_ go on without the OS ever
knowing what's happening (but all RAID cards come with monitor programs
so the OS can know what's going on and take appropiate action (ie,
disable web input to limit disk writes until the drive is replaced-the
server still functions, but in a limited sort of way which prevents
further problems))

Many, if not most, RAID cards will handle this sort of situation.
Generally you'll spend about $40 to $100 for each drive bay (these are 5
1/4 units which hold 3.5 inch drives), and (depending on the bus and
model) you'll spend anywhere from $30 to $500 for a RAID card.

For your situation a simple RAID 0 (mirroring only) would suffice.  It
is especially good for web serving as RAID 0 reads twice as fast (since
it can read from both drives at once) than a single HD would (though
writing takes place at the same speed as the slowest drive in the RAID).

-Adam


James Newton wrote:
{Quote hidden}

> {Original Message removed}

2001\02\14@005357 by Sean H. Breheny

face picon face
I think that you can buy SCA-equipped Quantum drives from Quantum's online
store.

Sean

At 10:19 PM 2/13/01 -0600, you wrote:
{Quote hidden}

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2001\02\14@005911 by David VanHorn

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face
>
>Yes, but without power sequencing and disconnection you risk _physical_
>damage to any and all devices attached to the bus.

That's just a physical connector problem. Disconnect the SCSI bus (only 5V
and ground there, lots of ground...) then pull the power.
A function either of the owner's fingers, or the drive bay hardware.


> > Been there, done that, wrote the code myself.
> > This is kind of like the W95 version of SCSI which didn't support LUNs.
> > Apparently MS didn't feel like implementing that part of the spec, so they
> > just tossed it out.
>
>Of course the fact that almost nobody ever used LUNs (the only exception I
>know of is an ancient Bournoulli box) might have something to do with it.

CDROM changers, and even some Adaptec SCSI interfaces used it.



> > SCSI also supports multiple computers on the bus, but Adaptec's software
> > dosen't do that either.
>
>Again, not some often used.

They did say "Small Computer System Interface"
not "Cheesy Hard Drive Interface".

My SCSI bios for the Ampro was 8k. Full Bios, plus multi-initiator
arbitrating SCSI with LUN support.  Had two CPUs running off the same hard
drive in '84.
Network hardware was $$$ then, and the software wasn't far behind either.


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2001\02\14@010224 by David VanHorn

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face
>
>
>Chuckle...  Thought I'd choke on my coffee, I was laughing so hard.

You heard that they are rolling out yet another try at an OS late this
year?  The idea is to take the best points of NT, CE, and ME, and put them
all together in one place.

Windows CE ME NT


(I''ve taken to re-arrainging books in bookstores, I wonder if anyone gets
it.. :)

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2001\02\14@011040 by David VanHorn

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At 09:21 PM 2/13/01 -0600, Mitch Miller wrote:
>That's not entirely true ... while the SCSI protocol may allow drives to
>come and go, you still have to consider the electrical interface.  You can't
>(practically speaking) just open your case and pull the cable from a drive.
>Most hot-swapping drive bays connect the power (at least the GND) lead prior
>to the signals.  I believe PCMCIA and CARDBUS cards do the same.


Totally a mechanical issue.

What's so hard about a drive bay that jacks out the SCSI connector before
the power connector begins to break?

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2001\02\14@012941 by mmucker

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>
> SCSI also supports multiple computers on the bus, but Adaptec's software
> dosen't do that either.
>

AAIIGGHH!

David, don't give these people ideas!

Folks, don't put multiple controllers on the same SCSI bus unless you really
know what you're doing.  (I've supported too many customers who didn't.)

Yes, SCSI works just fine with multiple host adapters on the bus.  IF you
know what you're doing.  And I have the Microsoft Cluster Server up and
running to prove it.  :)

And David is also correct that SCSI is natively hot pluggable.  The main
things those fancy-schmancy hot swap bays do is that they provide longer
power pins than data pins, so that as you slide the drive in, the power gets
connected before the data lines, which prevents noise.

Right, David?

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2001\02\14@015116 by David VanHorn

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>
>I have a 7-disk CD changer with a separate LUN for each disk.  Best
>impulse purchase I've ever made...  Had to patch freebsd to get it to work
>right there, though.  W98 handles it fine by default, I think.


At one time, I had a web page up on that issue with Win95 explaining the
truth of the issue. MS's "help" line was giving out all sorts of bullshit
like that LUNs weren't part of SCSI, etc, etc.. At one point someone from
MS called up my boss and raised hell with him, threatened to sue (don't
know why he thought my boss was involved..) Later they dropped it, and in
'98 it was fixed.

It's not hard to write.

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2001\02\14@015330 by David VanHorn

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>
>AAIIGGHH!
>
>David, don't give these people ideas!
>
>Folks, don't put multiple controllers on the same SCSI bus unless you
>really know what you're doing.  (I've supported too many customers who didn't.)

He's right folks.
I doubt you'll find anything around these days that supports multi-initiator.
It's supposed to be there, it's part of the spec, but apparently them who
sell the software don't feel like implementing it.

(I did say their controllers don't do it either...)

>Yes, SCSI works just fine with multiple host adapters on the bus.  IF you
>know what you're doing.  And I have the Microsoft Cluster Server up and
>running to prove it.  :)

Where did you find the software, or did you write it?

>And David is also correct that SCSI is natively hot pluggable.  The main
>things those fancy-schmancy hot swap bays do is that they provide longer
>power pins than data pins, so that as you slide the drive in, the power
>gets connected before the data lines, which prevents noise.

Yup.  :)


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2001\02\14@020125 by Bill Westfield

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> Probably.  SCA is an 80-pin connector that carries power, SCSI signals,
> drive ID, everything on one conenctor.  They are only made as OEM devices,
> to me knowledge no drive manufacturer sells them to consumers.

Sort of accademic, since many "retailers regularly resell the OEM versions
of drives to anyone with the $$$ (Fry's, Disk Drive Depot, Outpost.com, most
PC shops, etc, etc.)

BillW

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2001\02\14@090908 by Dale Botkin

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On Tue, 13 Feb 2001, William Chops Westfield wrote:

> > Probably.  SCA is an 80-pin connector that carries power, SCSI signals,
> > drive ID, everything on one conenctor.  They are only made as OEM devices,
> > to me knowledge no drive manufacturer sells them to consumers.
>
> Sort of accademic, since many "retailers regularly resell the OEM versions
> of drives to anyone with the $$$ (Fry's, Disk Drive Depot, Outpost.com, most
> PC shops, etc, etc.)

To be sure... but you want to make sure what the support issues are before
buying.  I have heard of cases (no first hand knowledge, but it sounds
like what drive manufacturers often do) of people not being able to get
support from manufacturers, who tell them to go to the OEM who they made
the drive for.

Dale
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2001\02\14@172355 by Peter L. Peres

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Internal hard drives are almost never hot-swappable (even if RAIDed).
Hot-swappable drive bays usually have a special separator/protector (an
array of FETs cutting all the wires to the drive from the bus) and a sense
switch to sense the hot-swapping. Some also have a electromechanical lock
that refuses to release the drive if the system is using it for something
else than you think it does. The easiest way to spot them is the price tag
for the racks ;-)

Peter

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2001\02\15@024705 by Lee Jones

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>> In a RAID system, are standard drives "Hot Swappable"?

Define "standard drives".  If you mean SCSI with SCA style
connectors in an enclosure designed for it, then yes, they
always are.  If SCA in an enclosure not designed for it,
then no, they usually aren't.

If you mean standard 50-pin (narrow) or 68-pin (wide) SCSI
drives with seperate I/O connectors, power connectors, and
SCSI ID jumpers, then probably not.  The enslosures designed
for these almost never provide the slide-in/slide-out trays
that make it practicle.  Assuming you could live with that,
you could try hot swapping with some risk as follows:

To remove a "bad" drive:

   1) remove SCSI I/O connector (68 or 50 pin) at drive
   2) remove power connector from drive
   3) unbolt drive & remove from enclosure

To install a "good" drive, set it's SCSI ID to a known good
value and reverse above procedure.  If the drives are powered
from the same power supply as the system board, expect a 50%
chance of a system crash when you plug the power connector
into the replacement drive.


> The "Hot swappable" drives I was referring to are SCA drives.
> SCA refers to Single Connector Attach. From what I can tell,
> SCA means that the last device on the bus will automatically
> terminate. Sorry, I'd had SCA described as hot swappable by
> our supplier when they're not quite the same.

SCA is an 80-pin SCSI connector system where the I/O lines,
the power & ground lines, and the SCSI ID lines are all on
a single thin D style connector.  SCA is always 16-bit wide
SCSI.  It's main reason for existance was to make it easy to
build enclosures that allow for hot swapping.

SCA drives never terminate the bus.  They never provide any
termination options.  End of the bus, usually a PC board for
SCA drives, provide termination.  I agree with this philosophy.
If at all possible, I always terminate the SCSI bus in the
enclosure or cable end (not in any drive itself).


Sometimes the drive enclosure can add hot-swap capability
to any drive.  Take a look at Kingston's Data Silo products.
The DS500 tower is very nicely made.

The DE300 enclosure bays are wonderfull.  Each DE300 bolts
into a 5.25" full height drive bay.  Each DE300 has 3 trays;
each tray holds a 1" high 3.5" form factor drive.  The SCSI
drive can be either SCA or normal 68-pin wide.  The trays
can allow hot swap.

So what's the downside?  Well, let's say you have six 18GB
wide SCSI drive at $330 each (US price) -- total $2,000.
A DS500 with 2 DE300s will add about $1,000 to the price
tag.  Yes, 50% premium.  But it will do hot swap and has
dual, redundant power supplies.  It's solid as a brick.
(And weighs as much; moving a loaded DS500 tower under a
table in a server room is a bitch.)

Alternately, buy 7 drives and an Antec 9 bay SCSI enclosure.
Total is about $2,500.  No redundant power.  No hot swap.
But you do have a hot spare drive available whenever needed.

Or buy one of the RAID ready, hot swap enclosures on Ebay.
Look for name brand enterprise level equipment, usually it
was rack mounted, being sold used.  They tend to be older
with lower capacity 4GB or 9GB drives, but that might be
acceptable.

This all pre-supposes that you have a RAID controller or
RAID software that can operate in degraded mode with one
failed drive and then rebuild the RAID set after a new
drive has been added (either hot-swap, hot spare, or after
a power-cycle drive replacment).  Mylex RAID controllers
do this very well, aren't too expensive new, are available
at reasonable prices on Ebay, and are supported by almost
everybody (Windows NT, Linux, VMS, Digital Unix, etc).

I can provide more details on request.
                                               Lee Jones

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