USB powered extrnal hard drives

[just bob]

Is it widely accepted that USB-powered hard drives are slower than AC-power
hard drives?

I have a Seagate 100GB External USB 2.0, USB-powered, hard drive which does
not seem very fast. That is, even if I plug in the both the USB+Data cable
and USB+Power cable and it is just not as fast as an external hard drive
which draws power from an AC power supply.

I can't seem to find any information on the transfer speed from
www.seagate.com, only that the drive is 5400 RPM and 8MB cache.

Thank you,
-Bob

 

[just bob]

Also I can't seem to find information.on whether the optional AC adapter for
this unit would help transfer speed or if it is only for when you have a PC
which does not support USB power.

Thanks again

 

[Jesco Lincke]

Is it widely accepted that USB-powered hard drives are slower than AC-power
hard drives?

I have a Seagate 100GB External USB 2.0, USB-powered, hard drive which does
not seem very fast. That is, even if I plug in the both the USB+Data cable
and USB+Power cable and it is just not as fast as an external hard drive
which draws power from an AC power supply.

I can't seem to find any information on the transfer speed from
www.seagate.com, only that the drive is 5400 RPM and 8MB cache.

Thank you,
-Bob

Well, the Datasheet says they support 480Mbit/s (60MB/s, which ist the
max. USB 2.0 transfer rate). It does not say that the drive PROVIDES
those rates.

Which gives me a thought...you ARE operating the drive on a USB 2.0
port, aren't you? Just making sure...

So:

The benchmarks on the following page suggest an average read-only rate
of 200Mbit/s (25MB/s), and an average write-only of 120Mbit/s (15MB/s).
Data copying within the drive can go as low as 56Mbit/s (7MB/s) - all in
a FAT32-system, NTFS makes it even worse...

http://www.xbitlabs.com/articles/storage/display/seagate-usb20_5.html

Another page quotes:

"To test the drive I copied a DVD sized amount of data - 4.41GB to be
precise. This took four minutes and 10 seconds to copy across to the
100GB Seagate drive. Reading the same data back to the desktop PC took a
less impressive six minutes and 21 seconds[...]"

http://www.trustedreviews.com/storage/review/2005/04/01/Seagate-100GB-USB-2-0-Portable-hard-drive/p2

Which means roughly 18MB/s write and 12MB/s read, so no big difference
here...

Does that match you experience?

Jesco

 

[Rod Speed]

Is it widely accepted that USB-powered hard drives are slower than AC-power hard drives?

Only in the sense that only laptop drives can be USB powered
and they are certainly slower and more expensive than the best
3.5" desktop drives that cant be USB powered.

I have a Seagate 100GB External USB 2.0, USB-powered, hard drive which does not seem very fast.
That is, even if I plug in the both
the USB+Data cable and USB+Power cable and it is just not as fast as
an external hard drive which draws power from an AC power supply.

Because its only got a laptop drive in it, and those
are noticeably slower than current desktop drives.

I can't seem to find any information on the transfer speed from
www.seagate.com, only that the drive is 5400 RPM and 8MB cache.

The transfer speed isnt that easy to measure properly.

Just time the transfer of a large file manually,
and time the transfer of a folder of smaller files manually.

Also I can't seem to find information.on whether the optional AC adapter for this unit would help
transfer speed

No it wont.

or if it is only for when you have a PC which does not support USB power.

Or not enough USB power. All do provide at least minimal USB power.

 

[Arno Wagner]

Is it widely accepted that USB-powered hard drives are slower than
AC-power hard drives?

They are not. However only 2.5" drives and smaller can be USB powerd
and for some 2.5" drives the power USB can deliever is still
not enough.

With AC power you can use 3.5" drives, and they are significantly
faster.

I have a Seagate 100GB External USB 2.0, USB-powered, hard drive
which does not seem very fast. That is, even if I plug in the both
the USB+Data cable and USB+Power cable and it is just not as fast as
an external hard drive which draws power from an AC power supply.

I can't seem to find any information on the transfer speed from
www.seagate.com, only that the drive is 5400 RPM and 8MB cache.

Some _very_ rough numbers:

2.5", 5400 rpm, HDD: 20MB/s sustained
3.5", 7200 rpm, HDD: 60MB/s sustained

USB: 20-40 MB/s sustained

Arno