Conference decwet::advfs_support

1059.0. "Increment defrag's, defrag resource usage" by DV780::ENGQUIST (Eric Engquist) Mon May 12 1997 21:53

    I am curious how defragment works.  We have a large domain
    that takes anywhere from 14 hours to 2-1/2 days to defragment.
    It is about 16GB and is lots of programs.  I suspect that some
    of these long defrags took so long as they were waiting for
    dumps to finish.  Anyway, instead of doing a large defrag
    each weekend, we want to look at doing it a hour or two
    a day.  I suspect defrag works by finding fragments and 
    fixing those, hence the next day it would have to defrag
    some of what was already defrag'ed the day before if that
    changed and then continue on to new files.  Does this sound
    correct?  What have you noticed on how long defrag's take?
    Are incremental defrag's the way to handle this?  In addition,
    one person in my group noticed that the defrag's were the
    only thing running, yet they were using 85% of the cpu time.
    This sounds high, I would think that they would be more I/O
    bound.  Lastly do you have an idea of how much memory resources
    a defrag would use?
    
    Thanks for any answers