SATA "II" external HDD enclosures - 150 or 1500 Mbps data transfer

I'm going to build an external SATA 300GB to 500GB HDD for data backup.
The biggest attraction of SATA for me is the 1500Mbps data transfer
rate (3 times faster than USB 2.0) .

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps. The
only
enclosure I've found that advertises 1500 is this one:

http://www.satagear.com/USBG-SATA-35...rive_Case.html

All of these say either 150, or don't say:

http://www.newegg.com/Product/Produc...ta&order=price

Are the "150's" merely typos, or is it important to ensure that an
external SATA HDD enclosure supports 1500 Mbps, not just 150 Mbps?

PJ wrote

I'm going to build an external SATA 300GB to 500GB HDD
for data backup. The biggest attraction of SATA for me is the
1500Mbps data transfer rate (3 times faster than USB 2.0) .

In practice you will be limited to what the drive itself can do
and that interface speed is almost completely academic.

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps.
The only enclosure I've found that advertises 1500 is this one:
http://www.satagear.com/USBG-SATA-35...rive_Case.html

All of these say either 150, or don't say:
http://www.newegg.com/Product/Produc...ta&order=price

Are the "150's" merely typos,

Very unlikely indeed that so many would have the same typo.

or is it important to ensure that an external SATA HDD
enclosure supports 1500 Mbps, not just 150 Mbps?

Nope, in practice the speed you see will be determined by the
physics of the drive, the rotation rate and sectors per track.

PJ wrote:

I'm going to build an external SATA 300GB to 500GB HDD for data backup.
The biggest attraction of SATA for me is the 1500Mbps data transfer
rate (3 times faster than USB 2.0) .

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps. The
only
enclosure I've found that advertises 1500 is this one:

http://www.satagear.com/USBG-SATA-35...rive_Case.html

All of these say either 150, or don't say:


http://www.newegg.com/Product/Produc...ta&order=price

Are the "150's" merely typos, or is it important to ensure that an
external SATA HDD enclosure supports 1500 Mbps, not just 150 Mbps?

Are you sure you're not misreading 150 mega_bytes_/sec as 150
mega_bits_/sec?

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

OK, thanks. So since the interface speed of the enclosure (claimed
150Mbps) is nearly academic, if the SATA HDD drive claims 1500Mbps, I
shouldn't worry about being limited to what the enclosure speed claims.
Am I on track with this conclusion?

Rod Speed wrote:
PJ wrote

I'm going to build an external SATA 300GB to 500GB HDD
for data backup. The biggest attraction of SATA for me is the
1500Mbps data transfer rate (3 times faster than USB 2.0) .

In practice you will be limited to what the drive itself can do
and that interface speed is almost completely academic.

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps.
The only enclosure I've found that advertises 1500 is this one:
http://www.satagear.com/USBG-SATA-35...rive_Case.html

All of these say either 150, or don't say:
http://www.newegg.com/Product/Produc...ta&order=price

Are the "150's" merely typos,

Very unlikely indeed that so many would have the same typo.

or is it important to ensure that an external SATA HDD
enclosure supports 1500 Mbps, not just 150 Mbps?

Nope, in practice the speed you see will be determined by the
physics of the drive, the rotation rate and sectors per track.

PJ wrote:
I'm going to build an external SATA 300GB to 500GB HDD for data
backup. The biggest attraction of SATA for me is the 1500Mbps data
transfer rate (3 times faster than USB 2.0) .

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps.

The key is in the capitalisation, or should be. SATA 1 is 1500 mbits/sec,
which comes out to 150 mbytes/sec after signalling overhead is taken into
account (10 bits required to send an 8-bit byte). The first can be
abbreviated to 1500Mbps, the second becomes 150MBps using the same style.
However, the capitalisation is lost or just done incorrectly in many cases
which leads to a bit of confusion.

Fortunately, there is no 1500MBps nor 150Mbps SATA. There's only 150MBps
(1500Mbps) and 300MBps (3000Mbps) variants, so you can easily see which is
which.

Note that you can get FireWire-800 (aka 1394b) hard disk enclosures which
would be more than fast enough for any current SATA drive, and offer some
other advantages such as longer cable length (4.5m vs 1m for SATA) and not
having to do any work to build it

[...]

--
Michael Brown
Add michael@ to emboss.co.nz ---+--- My inbox is always open

"PJ" wrote in message
ups.com...
OK, thanks. So since the interface speed of the enclosure (claimed
150Mbps) is nearly academic, if the SATA HDD drive claims 1500Mbps, I
shouldn't worry about being limited to what the enclosure speed claims.
Am I on track with this conclusion?

It sounds like you are getting closer to the real truth. Even if the HDD
itself advertises "1500Mbps" on the box, don't be fooled. There is no
consumer hard drive that is capable of data rates that high, heck I don't
know if there is a hard drive in existence that can sustain rates like that
(roughly 150 MEGABYTES per second). I have seen plenty of ATA100 hard
drives sold in stores with big giant banners on the boxes saying "100MBs
transfer rate" or similar. You must really, REALLY get down into the
manufacturers data sheets on their websites to find something that indicates
the specific drives capabilities which may be down in the neighborhood of
30-40MBs.

The point is, you can put a hard drive in a new fancy schmancy enclosure
that claims 500,000MBps and it won't make your transfers any faster if the
drive is only capable of 40MBps rates. Hard drives have gotten a bit faster
over the last few years but not as fast as the folks in marketing would lead
you to believe. With the latest drive interfaces that have become mainstream
over the last couple years the hard drive is almost always the bottleneck.

--Dan

PJ wrote in message
ups.com...

OK, thanks. So since the interface speed of the enclosure
(claimed 150Mbps) is nearly academic, if the SATA HDD drive
claims 1500Mbps, I shouldn't worry about being limited to what
the enclosure speed claims. Am I on track with this conclusion?

Yep, basically any SATA will be good enough currently,
because its the drive itself that limits the thruput in your situation.


Rod Speed wrote
PJ wrote

I'm going to build an external SATA 300GB to 500GB HDD
for data backup. The biggest attraction of SATA for me is the
1500Mbps data transfer rate (3 times faster than USB 2.0) .

In practice you will be limited to what the drive itself can do
and that interface speed is almost completely academic.

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps.
The only enclosure I've found that advertises 1500 is this one:
http://www.satagear.com/USBG-SATA-35...rive_Case.html

All of these say either 150, or don't say:
http://www.newegg.com/Product/Produc...ta&order=price

Are the "150's" merely typos,

Very unlikely indeed that so many would have the same typo.

or is it important to ensure that an external SATA HDD
enclosure supports 1500 Mbps, not just 150 Mbps?

Nope, in practice the speed you see will be determined by the
physics of the drive, the rotation rate and sectors per track.

Doubtless that's what my problem was: misreading the 'b' for a 'B', or
vice versa. Thanks.

I think I'll just opt for the 1.5GB/sec and be done with it. Or is
that bits.....

PJ wrote:

Doubtless that's what my problem was: misreading the 'b' for a 'B', or
vice versa. Thanks.

I think I'll just opt for the 1.5GB/sec and be done with it. Or is
that bits.....

Bits.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

"Michael Brown" wrote in message
PJ wrote:
I'm going to build an external SATA 300GB to 500GB HDD for data
backup. The biggest attraction of SATA for me is the 1500Mbps data
transfer rate (3 times faster than USB 2.0) .

It seems, however, that most external enclosures for SATA HDDs
advertise a 150Mbps data transfer rate, as opposed to 1500Mbps.

The key is in the capitalisation,

You don't say.

or should be.

SATA 1 is 1500 mbits/sec,

1500 Mb/s

which comes out to 150 mbytes/sec

150 Mbytes/sec

after signalling overhead is taken into account (10 bits required to send an 8-bit byte).

The first can be abbreviated to 1500Mbps,

Now you got it.

the second becomes 150MBps using the same style.

Right.

However, the capitalisation is lost or just done incorrectly in many cases
which leads to a bit of confusion.

Yup, you included.


Fortunately, there is no 1500MBps nor 150Mbps SATA. There's only 150MBps
(1500Mbps) and 300MBps (3000Mbps) variants, so you can easily see which
is which.

Note that you can get FireWire-800 (aka 1394b) hard disk enclosures which
would be more than fast enough for any current SATA drive, and offer some
other advantages such as longer cable length (4.5m vs 1m for SATA) and not
having to do any work to build it

[...]