Help Understanding Log Files - Veritas Volume Manager

This is a discussion on Help Understanding Log Files - Veritas Volume Manager ; I had been lead to believe that the Veritas Journaling File System was a separate purchase item. I was surprised to see after installing Volume Manager 3.1 for Windows that a log was created on one of the two mirror ...

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Thread: Help Understanding Log Files

  1. Help Understanding Log Files

    I had been lead to believe that the Veritas Journaling File System was a
    separate purchase item. I was surprised to see after installing Volume
    Manager 3.1 for Windows that a log was created on one of the two mirror
    drives. This certainly implies some form of journaling. What features
    does the Veritas File System enable beyond whatever the logfile in 3.1
    creates?

    Can someone explain to me is there any point in having redundant logfiles?

    Also, since the logfile appears to be a separate partition on the drive, I
    guess it doesn't matter whether mirror on the drive that contains the
    logfile is the mirror that is broken, and the logfile will continue to
    maintain new writes to the primary partition?

    --
    Will
    westes AT earthbroadcast.com



  2. Re: Help Understanding Log Files

    To check if the file system is installed, check for a package called
    "VRTSvxfs" . You can also check if there is such a module loaded in memory
    (modinfo | grep -i vx)



    Volume Manager also has logs (not just the file system).

    The log on a filesystem is normally only singular and part of the filesystem
    (unless you know where to go and look inside the filesystem, you will never
    see it). I suspect this is a Volume Manager log (You saw it in vxprint
    output ?)

    Now, the purpose of having more than 1 log file is simple.

    Depends on the type of log, but it might be used in speeding up the mirror
    process (by just keeping a list of blocks that needs to be mirrored, thus
    those changed, that still needs to change on the other disk - this will
    happen in the background, while your application writing to the disk, got an
    acknowledgement already from the "disk" to say that it could continue). If
    this journal is no longer there (ie. disk is failing - bad block where the
    journal is supposed to be), you have a backup (so you don't have to mirror
    your whole 1TB LUN.)
    This feature is called Fast Mirror Resync (FMR).

    The other important thing to remember is that Volume Manager does not have
    the typical "original" and "mirror" concepts. Please read the Admin Guide
    for the explanation of plexes, and where the data will actually be written.
    You will see that Volume Manager will switch the writes to the different
    disks (or you can set it). Thus, any disk can be the "original" and any disk
    can be the "mirror". Thus another reason to have 2 logs.



    ..
    "CHANGE USERNAME TO westes" wrote in
    message news:412656a9@ROSASTDMZ05....
    > I had been lead to believe that the Veritas Journaling File System was a
    > separate purchase item. I was surprised to see after installing Volume
    > Manager 3.1 for Windows that a log was created on one of the two mirror
    > drives. This certainly implies some form of journaling. What

    features
    > does the Veritas File System enable beyond whatever the logfile in 3.1
    > creates?
    >
    > Can someone explain to me is there any point in having redundant logfiles?
    >
    > Also, since the logfile appears to be a separate partition on the drive, I
    > guess it doesn't matter whether mirror on the drive that contains the
    > logfile is the mirror that is broken, and the logfile will continue to
    > maintain new writes to the primary partition?
    >
    > --
    > Will
    > westes AT earthbroadcast.com
    >
    >




  3. Re: Help Understanding Log Files

    To check if the file system is installed, check for a package called
    "VRTSvxfs" . You can also check if there is such a module loaded in memory
    (modinfo | grep -i vx)



    Volume Manager also has logs (not just the file system).

    The log on a filesystem is normally only singular and part of the filesystem
    (unless you know where to go and look inside the filesystem, you will never
    see it). I suspect this is a Volume Manager log (You saw it in vxprint
    output ?)

    Now, the purpose of having more than 1 log file is simple.

    Depends on the type of log, but it might be used in speeding up the mirror
    process (by just keeping a list of blocks that needs to be mirrored, thus
    those changed, that still needs to change on the other disk - this will
    happen in the background, while your application writing to the disk, got an
    acknowledgement already from the "disk" to say that it could continue). If
    this journal is no longer there (ie. disk is failing - bad block where the
    journal is supposed to be), you have a backup (so you don't have to mirror
    your whole 1TB LUN.)
    This feature is called Fast Mirror Resync (FMR).

    The other important thing to remember is that Volume Manager does not have
    the typical "original" and "mirror" concepts. Please read the Admin Guide
    for the explanation of plexes, and where the data will actually be written.
    You will see that Volume Manager will switch the writes to the different
    disks (or you can set it). Thus, any disk can be the "original" and any disk
    can be the "mirror". Thus another reason to have 2 logs.



    ..
    "CHANGE USERNAME TO westes" wrote in
    message news:412656a9@ROSASTDMZ05....
    > I had been lead to believe that the Veritas Journaling File System was a
    > separate purchase item. I was surprised to see after installing Volume
    > Manager 3.1 for Windows that a log was created on one of the two mirror
    > drives. This certainly implies some form of journaling. What

    features
    > does the Veritas File System enable beyond whatever the logfile in 3.1
    > creates?
    >
    > Can someone explain to me is there any point in having redundant logfiles?
    >
    > Also, since the logfile appears to be a separate partition on the drive, I
    > guess it doesn't matter whether mirror on the drive that contains the
    > logfile is the mirror that is broken, and the logfile will continue to
    > maintain new writes to the primary partition?
    >
    > --
    > Will
    > westes AT earthbroadcast.com
    >
    >




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