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raw devices, how to? - Oracle Server

NorwoodThree wrote: > Doesnt the OS realize the filesystem type (raw) and act accordingly? I've no idea but I thought that oracle somehow doesn't use the fs system calls. If it still seeks and tells, what's the use? Lots of Greetings! Volker -- While it is a known fact that programmers never make mistakes, it is still a good idea to humor the users by checking for errors at critical points in your program. -Robert D. Schneider, "Optimizing INFORMIX Applications"...

  1. #1

    Default Re: raw devices, how to?

    NorwoodThree wrote:
    > Doesnt the OS realize the filesystem type (raw) and act accordingly?
    I've no idea but I thought that oracle somehow doesn't use the fs
    system calls. If it still seeks and tells, what's the use?

    Lots of Greetings!
    Volker
    --
    While it is a known fact that programmers
    never make mistakes, it is still a good idea
    to humor the users by checking for errors at
    critical points in your program.
    -Robert D. Schneider, "Optimizing INFORMIX
    Applications"



    Volker Hetzer Guest

  2. #2

    Default Re: raw devices, how to?

    "Volker Hetzer" <volker.hetzerieee.org> wrote in message
    news:bdu8in$8am$1news.fujitsu-siemens.com...
    > I've no idea but I thought that oracle somehow doesn't use the fs
    > system calls. If it still seeks and tells, what's the use?
    >
    IIRC, it uses the read() and write() low-level I/O calls,
    regardless of file being cooked or raw. What determines
    if file is raw or not is the device name itself, which has
    to be opened as a file and associated with a file unit
    for use with the above calls, using the normal fopen().
    Unix drivers then use raw addressing instead of asynch
    Unix buffer indirection. There is a flag on ioctl block
    that defines if file has raw or cooked access.

    IOW, it's handled by Unix I/O mechanism itself. Not
    a different I/O call by Oracle. Although direct buffer
    offset access is of course then not possible. On the
    other hand, I/O goes directly to the SGA instead of to
    the Unix buffer cache. Which saves CPU and memory cycles
    copying buffers between the two. Around 20% CPU save
    on a busy I/O system. Typically, if you keep a gander
    on the sar stats, you see the system wait counter drop
    significantly with raw I/O. With (hopefully) a corresponding
    jump in the user counter.

    --
    Cheers
    Nuno Souto
    [email]wizofoz2k.au.nosp[/email]am


    Noons Guest

  3. #3

    Default Re: raw devices, how to?

    Exactly...thats why I believe its handled by the OS.
    NorwoodThree Guest

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