Am 17.05.2014 11:58, schrieb Neil Bothwick: > On Sat, 17 May 2014 09:59:08 +0200, meino.cra...@gmx.de wrote: > >>> 3. Or you could use a sequential copy: >>> >>> cp -a /home /dev/sdb1/ && cp -a /home /dev/sdc1 > >> 3.) The files I want to copy are in the size of some GB each. So the >> cache isnt big enough to hold ALL files for the second part. > > Run the two copies simultaneously, start the first, switch to another > tab, start the second. That way the data for the second copy is always > the most recently cached. > > However, I expect the speed limit here may be the USB bus unless you are > using USB 3.0 drives on different buses. I was thinking about "how to make sure cache is used", and that two simultanious cp won't work, because the progress for the two cp will quickly diverge. But then I realized: there is no need to think about the read cache - the limiting factor is always the writing side, especially with USB! So IMO it doesn't matter at all how you do it!
I guess two simultaneous cp will be the same as two sequential cp, except if you have two separate USB-buses. Usually you have just one externally connectible, use "lsusb -t" to check. If you have less that 2 times the size of your files, IMO simultaneous cp will be worse, because Linux (don't know if USB-subsystem or cp) creates big buffers when cp'ing (check with "free -m"), and you'll probably get into memory trouble. Greetings, Daniel PS: Quickest way is always to open USB-case and plug SATA cable from motherboard into drive. With >80GB it's always worth the trouble. -- Get my PGP key at: * http://keyserver.ubuntu.com:11371/pks/lookup?op=get&search=0x837FB8B5BB9D4887 * $ gpg --recv-keys --keyserver keyserver.ubuntu.com 0xBB9D4887
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