Re: [tlug] USB3 hard disks

[Travis Cardwell <travis.cardwell@example.com>]

On 2014年06月01日 14:15, Darren Cook 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? Does anyone do something like this as
> part of their backup strategy? (No longer having RAID-1 on either my
> main notebook, or my backup device(s), is making me nervous.)

By "copy the entire contents," do you mean copying the whole drive using a
command like `dd`?  If so, here are a few ways to get an estimate of how
long it will take:

A fancy option is to monitor the progress of the copy using `pv` (which
Kalin recommended in his presentation), which will even show you a countdown:

    $ dd if=/dev/SRC | pv | dd of=/dev/DST

A faster option is to send a USR1 signal to `dd` that is running with a
well-chosen block size (chosen based on the buffer sizes of each drive):

    $ dd if=/dev/SRC of=/dev/DST bs=16MB

After some time to get a good estimate (~5 minutes?), find the process ID
of the above and send the process a USR1 signal to display the transfer
rate; in a separate terminal:

    $ ps ax | grep dd
    $ kill -USR1 $pid

Calculate an estimated time based on the transfer rate and the size of the
drive.

Perhaps something like `dd if=/dev/SRC bs=16MB | pv | dd of=/dev/DST
bs=16MB` would provide performance as well as convenience, but I have
never profiled it...

I (often) copied drives using `dd` long ago, but I do not like how the IO
ties up the computer for so long.  These days, I use a product like the
following to copy [SATA] drives without using a computer:

HDDコピー機能付きSATA - USB3.0変換ケーブル
http://www.yodobashi.com/%E3%82%B5%E3%83%B3%E3%83%AF%E3%82%B5%E3%83%97%E3%83%A9%E3%82%A4-SANWA-SUPPLY-USB-CVIDE4-HDD%E3%82%B3%E3%83%94%E3%83%BC%E6%A9%9F%E8%83%BD%E4%BB%98%E3%81%8DSATA-USB3-0%E5%A4%89%E6%8F%9B%E3%82%B1%E3%83%BC%E3%83%96%E3%83%AB/pd/100000001002073943/

That is probably not an option in your case, unless you can take the hard
drives out of the USB interface cases.

Cheers,

Travis