Re: dd(1) performance when copiing a disk to another

From: Patrick Proniewski (patpro_at_patpro.net)
Date: 10/03/05

  • Next message: Bruce Evans: "Re: dd(1) performance when copiing a disk to another" 
    Date: Mon, 3 Oct 2005 09:55:49 +0200
To: Eric Anderson <anderson@centtech.com>

    Hi Arne and Eric,

    >>> # atacontrol mode 0
    >>> Master = BIOSPIO
    >>> Slave = BIOSPIO

    >> Hmm... 0 seems to be the wrong ata... Thats why the output does
    >> not fit to SATA drives, I think...

    oups... I'll have to do it again with channels 2 and 3

    >>> # dd if=/dev/ad4 of=/dev/null bs=1m count=1000
    >>> 1000+0 records in
    >>> 1000+0 records out
    >>> 1048576000 bytes transferred in 17.647464 secs (59417943
    >>> bytes/sec)

    >> That seems to be 2 or about 2 times faster than disc->disc
    >> transfer... But still slower, than I would have expected...
    >> SATA150 sounds like the drive can do 150MB/sec...

    As Eric pointed out, you just can"t reach 150 MB/s with one disk,
    it's a technological maximum for the bus, but real world performance
    is well bellow this max.
    In fact, I've though I would reach about 50 to 60 MB/s.

    >>>> (Maybe you could find a way to copy /dev/zero to /dev/ad6
    >>>> without destroying the previous work... :-))
    >>>
    >>> well, not very easy both disk are the same size ;)

    >> I thought of the first 1000 1MB blocks... :-)

    damn, I misread this one... :)
    I'm gonna try this asap.

    > Instead of dd, why not use gmirror?

    I had no idea gmirror exists, but I'll continue with dd. It's a one
    time experiment.

    > Have you tried a smaller block size? What does 8k, 16k, or 512k do
    > for you? There really isn't much room for improvement here on a
    > single device.

    nop, I'll try one of them, but I can't do many experiments, the box
    is in my living room, it's a 1U rack, and it's VERY VERY noisy. My
    girlfriend will kill me if it's running more than an hour a day :))

    Pat
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  • Next message: Bruce Evans: "Re: dd(1) performance when copiing a disk to another"