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What is kjournald

Discussion in 'General Discussion' started by silvernetuk, Mar 22, 2003.

  1. silvernetuk

    silvernetuk Well-Known Member

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    Hi

    What is kjournald ?

    Regards,
    Garry
     
  2. trakwebster

    trakwebster Well-Known Member

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    kjournald is ...

    For a number of years, Linux has been using a file system called .ext2 -- I don't know why it's called that.

    It's a nice reliable file system. However, if you've ever lost power on a linux box instead of using an orderly shutdown, you know that when you turn it on everybody has to wait for a long time while the ext2 filesystem checks out everything carefully. That's a long, long time.

    Recently, a new version of the file system showed up, called cleverly enough .ext3. I suppose there was some improvement in it, I don't know, but the most unusual feature was that you could add 'journalling' to the ext3 filesystem.

    Journalling means that the file system keeps a journal of what changes it's making, as it goes along. And if you should ever lose power, when you come back up, the filesystem can just go get the last journal, and this means it doesn't have to check and recreate everything from scratch.

    The benefit to you is that it boots up quickly. There is also, I assume, more safety and accuracy when it's got a journal.

    The daemon which keeps the journal up to date is called kjournald. If you run 'top', you'll see kjournal is always running, and it pops up to the top regularly.

    The journalling is an *option* so I'd guess there are folks out there running ext3 who do not see kjournald running. But as I recall it can be added on later. RedHat manuals have details I think.

    I'm no expert, and if I've said anything poorly, please somebody correct me.
     
  3. AceWeb

    AceWeb Well-Known Member

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    trakwebster is correct. :D

    kjournald is basically the indexing task that is running indexing and balancing on the EXT3 file system. It is however, likes to eat up system resources for some periods of time. kjournald was the improvement in the EXT3 for the recovery process.

    EXT2 has better performance and slower reboot times, but EXT3 reduced the performance a little (by running kjournald) but speeds up the reboots and is better for recovery.
     
  4. silvernetuk

    silvernetuk Well-Known Member

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    Hi,

    Thank you for that :D

    Regards,
    Garry
     

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