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  1. #1
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    Unanswered: ASE affected by compress dump

    Adaptive Server Enterprise/12.5.0.3/EBF 11331 ESD#3/P/Sun_svr4/OS 5.8/rel12503/1933/32-bit/FBO/Fri Aug 1 05:40:57 2003

    Hi All,
    We seem to be experiencing performance problems on ASE when dumping using compression. We are guessing that this may have something to do with with backup server using the shared memory segment to do the compression as the dump and db devices are on different devices and the disk activity is less when using compression.
    Nevertheless the performance degradation is radical, and processes are taking 10 times longer to complete and backup server tuning seems to have little effect.

    My question is :
    1. Should this be considered expected behaviour ?
    2. Are there some ASE/backup server tuning parameters that can reduce the impact ?
    3. Is anyone else getting the same behaviour ?

    Otherwise I will have to raise a case with Sybase about this
    Thanks in advance
    Andy Sykes

  2. #2
    Join Date
    Nov 2002
    Location
    Switzerland
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    524
    Which compression ratio are you using ?
    Don't know the detail, but be sure that a compression proces is CPU consuming.

  3. #3
    Join Date
    Jan 2004
    Location
    Munich/Germany
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    Re: ASE affected by compress dump

    Backup server use a lot of CPU to comress the data, not really memory, but from testing I found out that if you use compression level higher than 6 (default) the performance degrade badly, and the space gained is insignificant. So check if this is the case.
    You can also change the default of shared memory - apparently the backup server is smart enough to use only what it thinks is necessary, so no harm in doing that any way. Do that by adding the "-m " parameter in your backup RUN file

    I quote the asesag.pdf
    "
    Backup Server determines the amount of shared memory available for each stripe by dividing the -m value by the configured number of service threads (-P parameter).

    Hope this helps


    Originally posted by AndyS
    Adaptive Server Enterprise/12.5.0.3/EBF 11331 ESD#3/P/Sun_svr4/OS 5.8/rel12503/1933/32-bit/FBO/Fri Aug 1 05:40:57 2003

    Hi All,
    We seem to be experiencing performance problems on ASE when dumping using compression. We are guessing that this may have something to do with with backup server using the shared memory segment to do the compression as the dump and db devices are on different devices and the disk activity is less when using compression.
    Nevertheless the performance degradation is radical, and processes are taking 10 times longer to complete and backup server tuning seems to have little effect.

    My question is :
    1. Should this be considered expected behaviour ?
    2. Are there some ASE/backup server tuning parameters that can reduce the impact ?
    3. Is anyone else getting the same behaviour ?

    Otherwise I will have to raise a case with Sybase about this
    Thanks in advance
    Andy Sykes

  4. #4
    Join Date
    Dec 2003
    Location
    Amsterdam
    Posts
    4

    Re: ASE affected by compress dump

    Thanks for your replies. Actually we are using the default compression ratio (1) and I also tried the -m option with backupserver and it made very little difference.
    Andy

    Originally posted by stormnorm
    Backup server use a lot of CPU to comress the data, not really memory, but from testing I found out that if you use compression level higher than 6 (default) the performance degrade badly, and the space gained is insignificant. So check if this is the case.
    You can also change the default of shared memory - apparently the backup server is smart enough to use only what it thinks is necessary, so no harm in doing that any way. Do that by adding the "-m " parameter in your backup RUN file

    I quote the asesag.pdf
    "
    Backup Server determines the amount of shared memory available for each stripe by dividing the -m value by the configured number of service threads (-P parameter).

    Hope this helps

  5. #5
    Join Date
    Jan 2004
    Location
    Munich/Germany
    Posts
    12

    Re: ASE affected by compress dump

    This is strange I now see two specification in the manual for what is the default compression level:

    Here I see 6:
    The default compression level (6) provides optimal CPU usage, producing an archive that is 60 percent to 80 percent smaller than a regular uncompressed archive. Sybase recommends that you initially use the default compression level, then increase or decrease the level
    based on your performance requirements.

    and here I see 1:
    If you do not specify compression_level, the default is 1

    For more info on this check >> "System Administration Guide">> "Backing up and Restoring user databases">>"Specifying the compress option"

    I would try different level then 1, just as a test try the level 6, I had good results using that level.

    One final thought, maybe you have enough CPU power to utilize the 6 level, which generate smaller amount of data, which shrink the disk i/o size.


    Any way, good luck with fixing this issue, if I come across anything that might help, I will post it for you.



    Originally posted by AndyS
    Thanks for your replies. Actually we are using the default compression ratio (1) and I also tried the -m option with backupserver and it made very little difference.
    Andy
    Last edited by stormnorm; 01-14-04 at 09:29.

  6. #6
    Join Date
    Nov 2002
    Location
    Switzerland
    Posts
    524

    Re: ASE affected by compress dump

    The best compression ration is 4 or 5

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