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  1. #1
    Join Date
    Jan 2003
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    17

    Unanswered: Raw device in memory

    Has anyone ever created a raw device in memory and used it for tempdb. I have used and heard of Memory File Systems. But I have never used a raw device in memory before. We are running on a Regatta P670 and are doing some testing using this setup for tempdb. Just curious if anyone else has tried it before.

    Thanks,

    -Carl

  2. #2
    Join Date
    Sep 2002
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    Hong Kong
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    Re: Raw device in memory

    Interesting question. What benefits over a temp fs based tempdb device would you expect from a raw device?

  3. #3
    Join Date
    Jan 2003
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    17
    No Filesystem cache overhead. You can give more memory to ASE.

  4. #4
    Join Date
    Sep 2002
    Location
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    Originally posted by cdotger
    No Filesystem cache overhead. You can give more memory to ASE.
    I don't think tempfs is cached since it exists in memory. If you have enough memory and a version of ASE that supports it (ie 64 bit) configure a named cache for tempdb and use that.

  5. #5
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    Jan 2003
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    IBM support says it is. We are a very busy shop with alot of third party code that pounds tempdb. We want tempdb to be on the fastest device possible. Currently the log segment of tempdb is sucking up 6GB or file cache on the system. We want to eliminate that and add some memory back to ASE

  6. #6
    Join Date
    Sep 2002
    Location
    Hong Kong
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    Originally posted by cdotger
    IBM support says it is. We are a very busy shop with alot of third party code that pounds tempdb. We want tempdb to be on the fastest device possible. Currently the log segment of tempdb is sucking up 6GB or file cache on the system. We want to eliminate that and add some memory back to ASE
    Actually creating a raw device could be done provided a logical volume manager can be found to create them in memory and create the relevant device links.

    How about a solid state disk? This is probably the most supported route, although costly.

  7. #7
    Join Date
    Jan 2003
    Posts
    17
    Opened a case with sybase on 1/29/03. We were getting sddone and bufwritedes errors on the memory devices for tempdb log. Sybase reports that they do have customers running this same config with no issues. All you need to do is execute "mkramdisk size". Solid State is , like you stated, more costly but I would think also slower than a device in memory (raw).

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