Re: [tlug] USB3 hard disks

[Kalin KOZHUHAROV <me.kalin@example.com>]

On Sun, Jun 1, 2014 at 4:16 PM, Josh Glover <jmglov@example.com> wrote:
> On Sunday, 1 June 2014, Darren Cook <darren@example.com> wrote:
>
>> Quick question: I've two USB3 sockets. If I plug two hard disks in, and
>> want to copy the entire contents of one drive to the other drive,
>> roughly how long will it take?
>
>
> According to Wikipedia, [1] the transfer speed of USB 3.0 is 5 Gbps
> (gigabits), so if the source drive can read at 2.5 Gbps and the target drive
> can write at 2.5 Gbps, you can expect a minimum time of 54.61 minutes.
>
According to what I read in Wikipedia [1], "USB 3.0 has transmission
speeds of up to 5 Gbit/s", so paying attention to details, please note
"up to 5Gbps" and "transmission speeds", the latter meaning total
bandwidth, not transfer speed (usable part, your data only). USB is
notorious for overhead, the SS does alleviate the pain only a bit;
transferring many small files (i.e. not one bulk transfer) does shine
on the limitations.

[1] http://en.wikipedia.org/w/index.php?title=USB_3.0#Differences_in_comparison_to_USB_2.0

Standard drives these days rarely go above 100MB/s in native SATAII or
III. Problem is that various timings inside the drive and USB
interface (interpreting ATA commands coming from USB into SATA) end up
clogging the pipeline.

If you want to compare interface speed get one of the latest SSDs and
try read/write through USB3 and SATA.

Kalin.