Daniel Troeder <dan...@admin-box.com> [14-05-17 16:36]: > 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 >
Hi, thank you /.*/ for /.*/ replies ! :) ...one aspect is missing: The load (that is the I/O on the source hd). If this hd is busy spitting out the data twice, it cannot serve outhe jobs twice as long... Hmmmm.... Best regards, mcc PS: On the source system #> lsusb -t /: Bus 09.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/4p, 12M /: Bus 08.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/2p, 12M /: Bus 07.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/5p, 12M |__ Port 2: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M |__ Port 2: Dev 2, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M /: Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M /: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 480M /: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/5p, 12M |__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M |__ Port 3: Dev 3, If 0, Class=Audio, Driver=snd-usb-audio, 12M |__ Port 3: Dev 3, If 1, Class=Audio, Driver=snd-usb-audio, 12M /: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/4p, 480M /: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/5p, 480M /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/5p, 480M |__ Port 4: Dev 4, If 0, Class=Hub, Driver=hub/6p, 480M