Re: Very low disk performance on 5.x

From: Jonathan Noack (noackjr_at_alumni.rice.edu)
Date: 05/03/05

  • Next message: Jim C. Nasby: "Re: 64bit CPUs" 
    Date: Mon, 02 May 2005 17:16:44 -0500
To: Steven Hartland <killing@multiplay.co.uk>

    On 5/2/2005 4:56 PM, Steven Hartland wrote:
    > ----- Original Message ----- From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
    >> On -current and 5.4 you don't have to make partitions if you
    >> intend to use the entire disk (and provided you don't want
    >> to boot from it). You can simply:
    >>
    >> newfs /dev/da0
    >> mount /dev/da0 /where_ever
    >
    > /dev/da0: 1526216.3MB (3125691008 sectors) block size 16384, fragment
    > size 2048
    > using 8306 cylinder groups of 183.77MB, 11761 blks, 23552 inodes.
    > mount /dev/da0 /mnt
    >
    > dd if=/dev/zero of=/mnt/testfile bs=64k count=100000
    > 100000+0 records in
    > 100000+0 records out
    > 6553600000 bytes transferred in 44.424588 secs (147521908 bytes/sec)
    >
    > /usr/bin/time -h dd of=/dev/null if=/mnt/testfile bs=64k
    > count=100000 100000+0 records in
    > 100000+0 records out
    > 6553600000 bytes transferred in 48.150473 secs (136106658 bytes/sec)
    > 48.27s real 0.01s user 12.33s sys
    >
    > /usr/bin/time -h cat /mnt/testfile > /dev/null
    > 48.12s real 0.26s user 14.92s sys
    >
    > Raw read:
    > /usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k
    > count=100000 100000+0 records in
    > 100000+0 records out
    > 6553600000 bytes transferred in 32.028544 secs (204617482 bytes/sec)
    > 32.02s real 0.02s user 2.73s sys

    Look at the difference in sys times for raw vs. filesystem reads. With
    raw we're at 2.73s while reading from the filesystem requires 12.33s!
     From my position of complete ignorance that seems like a lot... 

    -- 
Jonathan Noack | noackjr@alumni.rice.edu | OpenPGP: 0x991D8195

  • Next message: Jim C. Nasby: "Re: 64bit CPUs"

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