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From:Benjamin Arai Date:January 13 2002 10:20am
Subject:Re: Database Size Limit
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I disagree.  The 4GB slowdown is usualy caused by indexing problems
associated with the OS having increased overhead when looking up and
inserting data.  I have eliminated this slowdown in Solaris and Linux be
re-indexing the entire database once it becomes larger then 4GB.  This
fixes the problem from what I could tell.

I would also like to note that if there was a pointer issue when switching
to 64 bit pointers, it would only effect perfomance on computer with less
then sufficent amounts of processing power to calculate the larger
pointers.

Benjamin Arai
benjamin@stripped

On Fri, 11 Jan 2002, James Montebello wrote:

>
> This is speculation:
>
> They're slower because many operations have to be done using 64 bit
> values rather than 32 bit values.  You set the flag by setting the max
> data size when creating the table.  You can also alter this after the
> table is created with ALTER TABLE.  The doc suggests you're setting the
> actual maximum size, but if you set the size to even 1 byte past 4GB
> (at least on Solaris), it immediately flips to a value way above 4GB,
> which is probably the Solaris limit (may be 2TB, I forget).  Not sure
> what it does on Linux.
>
> We saw a significant performance decrease on Solaris when we tried to
> use max table sizes above 4GB, and assume it's because of an internal
> switch from 32-bit pointers to 64-bit pointers.  May not make nearly as
> much of a performance difference on a real 64-bit processor and OS.
>
> james montebello
>
> On Fri, 11 Jan 2002, Aaron Brick wrote:
>
> > > Yes and no.  With 3.23, the MyISAM format will, by default, have a 4GB
> > > limit (32 bits).  You can set flags on the table to allow a 64-bit table,
> > > and you'll generally hit an OS or physical limitation long before you
> > > run out of space.  The downside of the 64-bit version is it's considerably
> > > slower.  Better to split large datasets up into sub-4GB units.
> >
> > why are operations on the >4GB tables slower?
> >
> > and, incidentally, where is that flag set?
> >
> > thanks,
> >
> > aaron brick.
> >
> >
> >                 ________________________________________________
> >                /                                                \
> >               |   Aaron Brick                 (415) 206 - 4685   |
> >               |   brick@stripped         Room 3501C, SFGH   |
> >
> >                   Programmer Analyst, Functional Genomics Core
> >                    Sandler Center for Basic Research in Asthma
> >                    Lung Biology Center, Department of Medicine
> >                                 San Francisco General Hospital
> >                        University of California, San Francisco
> >
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Thread
Database Size LimitManish Mehta11 Jan
  • Re: Database Size LimitDan Nelson11 Jan
    • Re: Database Size LimitJames Montebello11 Jan
      • Re: Database Size LimitAaron Brick11 Jan
        • Re: Database Size LimitJames Montebello11 Jan
          • Re: Database Size LimitBenjamin Arai13 Jan
Re: Database Size LimitDemirchyan Oganes-AOD09811 Jan
  • Re: Database Size LimitBenjamin Arai13 Jan
    • Re: Database Size LimitAaron Brick14 Jan
      • Re: Database Size LimitJeremy Zawodny17 Jan
Re: Database Size LimitHeikki Tuuri13 Jan