Re: Seeking information on SATA hard drive hot-swapping . . .
- From: "Anna" <myname@xxxxxxxxx>
- Date: Tue, 25 Apr 2006 12:21:20 -0400
(In response to Stan Shankman's query re "hot-plugging" SATA HDs)...
"Anna" <myname@xxxxxxxxx> wrote in message
news:Kv2dnT3dAIjgAtbZRVn-ug@xxxxxxxxxxxxxxx
I assume your reference to "drive sleds" refers to mobile racks designedto house removable hard drives.
capable.
Here's some general background information we've picked up over the past
year or so concerning "hot swapping" SATA hard drives...
Based on our contacts with the SATA-IO organization
(http://www.sata-io.org), the lead organization developing specifications
for the SATA-IO HDs, (the "IO" denoting "International Organization"),
formerly called SATA-II (and apparently still known by that latter
designation by most users), and a number of HD manufacturers, here's what
we've been able to glean re this "hot-plugging" issue as it applies to
SATA HDs...
There are two basic requirements for SATA hard drives to be
"hot-pluggable" (a/k/a "hot-swappable"), to wit...
1. The SATA HD must have this capability. The manufacturer must
*specifically* indicate that the particular drive is hot-pluggable
BTW, both the earlier SATA HDs having a data transfer rate of 1.5 Gb/s
and
the latest SATA-IO HDs having a data transfer rate of 3 Gb/s can be
hot-pluggable. According to the information we received from the SATA-IO
organization, the user cannot assume that merely because the drive is
designated SATA-IO (SATA-II) it is inherently hot-pluggable. It would
seem
that in theory this *should* be so presuming the drive meets SATA-IO
specifications, but we were cautioned not to make this assumption and as
indicated, contact the drive's manufacturer for verification.
2. The motherboard must support hot-plugging capability, i.e., its SATA
controller must provide hot-plugging support.
One other consideration...
SATA native hot plug as defined by the specification requires the use of
the 15-pin SATA power connector, *not* the 4-pin Molex power plug
commonly
used to connect IDE devices and frequently found on SATA HDs alongside
the
SATA power connector. Furthermore, the specification also calls for a
requirement that the power signal cables be connected/disconnected
*simultaneously* in order for native SATA hot plugging to be supported.
(In our >> case, we accomplish this by mounting the external SATA HDs in
the removable
tray/caddy in mobile racks so a simple push or pull on the removable
tray's handle simultaneously connects/disconnects both the power/signal
cables.)
I have to admit that every SATA-IO HD we've worked with for nearly a year
now (WD, Hitachi, Samsung, and Seagate, all SATA-IO drives) has proven to
be hot-pluggable. I would add that in many instances while experimenting
with
the hot-plugging capability of the afore-mentioned SATA drives while they
were connected as external devices, we've connected/disconnected the
drives without regard to any simultaneous connection or disconnection of
the data
& power connectors and we suffered no ill effects that we're aware of in
terms of data loss/corruption or damage to the drives. At least none to
date.
Even in cases where the SATA HD received its power through the Molex plug
we
didn't run into any problems, but we really did not do extensive testing
with that configuration. In nearly every case power was applied to the
SATA
HD though its 15-pin power connector.
Anna
"Stan Shankman" <stantheman@xxxxxxxx> wrote in message
news:124rrag184u85e3@xxxxxxxxxxxxxxxxxxxxx
More Information on SATA Hot-Plugging and Hot-Swapping
Anna,(SNIP)
So anyway, enough of my "dreaming". And now, if you wouldn't mind, I would
like to ask you a few questions.
Would you please explain in more detail how you go about swapping out a
disk? Do you use the Disk Management Console? Or what? What specifically
do
you do when you remove one drive and install another - and, for the
record,
are you talking about a RAID or not? Oh, and please specify which
operating
system you are using.
Now I would like to point-out; that of all the replies I have received so
far, no one has addressed the; "What makes a SATA controller
hot-pluggable?"
question. Is it just software? Or not?
And then finally, would you please state how satisfied you are with
hot-plugging. - Is it something you would defiantly recommend to others?
Thank you a lot for taking the time to answer these questions. I
appreciate
it very much. And I remind you that many more people will find your reply
on
Usenet from the Google search engine. And I am sure that they too will
thank
you for your wonderful information!
- Stan Shankman
Stan:
As I previously indicated, we usually work with removable HDs - what I
believe you were referring to as "drive sleds". This is still another
advantage of these "mobile racks" in that the user can simultaneously
connect & disconnect the power/signal cables from the SATA drives, thus
meeting the specification for "hot-plugging" capability of SATA hard drives.
The OS is XP in a non-RAID configuration. We haven't worked with SATA HDs to
any degree with prior operating systems.
There is no need to access Disk Management nor Device Manager (as I believe
one or more responders to your query indicated). Presumably when one is
invoking hot-plugging (hot-swapping), he or she is doing so with respect to
a secondary SATA HD. Obviously if the boot drive is disconnected the system
will go down and a reboot would be necessary. So, in the case of using
removable HDs in their mobile racks, it's a simple matter to disconnect the
secondary drive and substitute another in its place and the latter drive
will be recognized by the system. As simple as that.
While we're on this subject let me say a few words about a fairly recent
development which impacts on this hot-plugging (hot-swapping) issue...
A number of motherboards are now coming equipped with an eSATA ("e" for
external) port on the motherboard's backplane. By connecting an ordinary
SATA HD to this port (but note the eSATA port needs a special eSATA
connector on the signal/data cable that will be connected to it - see below)
you now have an *external* device that's treated as an *internal* device by
the system.
Think of the advantages of this. For the first time in an XP environment,
you will be able to directly install the XP OS onto an "external" SATA
drive, i.e., a drive that is physically located outside the computer's case,
and that drive will be bootable. So that the user could *directly* install
the XP OS onto that drive should he or she desire, or (possibly the more
common scenario) be able to clone the contents of one's internal day-to-day
working HD (PATA or SATA) - using a disk imaging program, e.g., Ghost, and
the drive will be bootable - a capability that has eluded us with
USB/Firewire external hard drives up to now. An enormous advantage, no?
Another advantage of using an "external" SATA HD is its speed. It will
operate substantially at the same speed as an internal SATA HD and thus be
considerably faster than a USB/Firewire EHD.
The eSATA port does allow for "hot-swapping" of connected devices assuming
the device itself has no problem with this capability.
Still another advantage of the eSATA port is that it supports the latest
SATA 3 Gb/sec specification.
Actually, you could connect a SATA HD to the eSATA port without the absolute
necessity of containing that drive in any special enclosure. Theoretically
you could plop it in a cigar box or even run the SATA data/signal cable
directly to a bare drive. Not the most desirable thing to do for the average
user, but it can be done. We generally set up our desktop computers with
mobile racks (2) to contain our removable hard drives. It's a hardware
arrangement that we strongly recommend for many desktop computer users. So
we usually contain the "external" SATA drive in one of the removable trays
that are also used in the mobile racks. And, as I previously indicated, this
hardware arrangement lends itself to simultaneous connects/disconnects of
the SATA HD to & from the system.
Now, what about the power to that SATA "external" drive? You simply use the
power from your computer's power supply. There's absolutely no need for an
external power supply. So that's another advantage of this eSATA device,
yes? It's a relatively simple matter for a user to run a power cable from
their PS to the external SATA drive, but it does mean that you have to snake
it out probably through one of the slots on the backplane of the computer's
case. On the other hand, enclosures are now coming onto the market with
direct SATA-to-SATA connection capability that have a built-in power supply.
A number of these now come equipped with eSATA connectors as well.
BTW, there's another device we came across that users may be interested in
to connect an external SATA HD. It's called the SATAPOWPLAT1, manufactured
or distributed by StarTech. Take a look at
$7.99 http://www.buy.com/retail/product.asp?sku=10360812&loc=101&sp=1 and
$5.45 http://www.provantage.com/scripts/cart.dll/x/0/rtspecs/STRT0HA
This device is simply attached to the I/O bracket on the computer case's
backplane. It comes with two external connectors - the SATA data connector
and the 15-pin SATA power connector. Internally (the other side of its slot
plate) is, of course, the SATA data connector and the normal 4-pin Molex
power plug. So it's a simple matter to connect the device to one of the
power leads of one's PS.
Given the significant advantages of an eSATA port connection I would guess
that more & more motherboards will be equipped with this feature since it
inherently has the substantial advantages of treating an "external" device
(the SATA HD) as a normal internal device together with providing superior
performance when compared with USB/Firewire external hard drives.
Our experience to date with "hot-plugging" has been very positive, both with
respect to using that feature with removable HDs and the eSATA feature as
noted above. As I previously stated, over the past year or so we've worked
with a fairly wide variety of SATA HDs and have experienced no problems
involving data corruption nor any physical problems affecting the drives
themselves.
Anna
.
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