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  1. #1
    Join Date
    Jan 2003
    Posts
    1,605

    Unanswered: Physical disk layout and DB2 containers. How to config?

    Hi,
    I am little bit confused. So far I have mainly worked with Intel servers and I know how RAID-5 arrays and physical disk is organized. When creating DB2 tablespace I know how to set containers to save data on multiple physical disks. So far so good.

    But know I should set-up tablespaces on Enterprise Storage Server (sharks) and DB2 v8.2fp11 database is running on Linux on System z server. I have been talking to system guy and he says that there is no such thing as "physical disk". System formats mini disks on 3 GB or 9 GB RAID disks arrays. Then this disks can be grouped together into Linux disk. Now my question is. I need 200 GB of disk space. What is better for DB2 performance to have multiple (for example 22 disks by 9 GB and therefore 22 tabespace containers) or only one 200 GB Linux disk with one tablespace container.

    Is there any settings to tell DB2 there are for example 22 disks grouped together into one Linux disk and I could still use one 200 GB disk?

    Is there any redbook or something like that where I could read more in detail how to set-up tablespaces (and containers) on RAID arrays on shark disks?

    Thanks,
    Grofaty
    Last edited by grofaty; 03-06-08 at 10:49.

  2. #2
    Join Date
    Jun 2003
    Location
    Toronto, Canada
    Posts
    5,516
    Provided Answers: 1
    Despite what your systems guy is saying, there is such thing as a physical disk (or volume). However, he's right that you should not be concerned with this. You should be thinking in logical volumes instead, which you see as separate devices but are in fact made of any number of physical volumes.

    There is no need to bother yourself with multiple containers when working with striped volumes, which will be the case in your situation. You will still want to distribute different types of tablespaces to different logical volumes though: temporary spaces should reside on volumes separate from those containing data.

    In brief the process should be something like this:
    - determine the number and sizes of logical volumes that you will need; e.g. one for each data, LOB, or index tablespace; one for each temporary tablespace; one small volume for logs; one for archived logs and on-disk bakcups; etc.
    - give this information to your systems guy, making sure that he understands which logical volumes must not share physical volumes, if you want maximum performance. There is no point in separating data and temp spaces if their logical volumes end up on the same physical disks. It is his task to make sure this does not happen;
    - once the logical volumes are defined and mounted, create tablespaces with 1 container each (unless you hit the physical limit on the container size).
    ---
    "It does not work" is not a valid problem statement.

  3. #3
    Join Date
    Jan 2008
    Posts
    88
    there are two parameters in this case...one is
    db2_PARALLEL_IO and db2_STRIPED_CONTAINERS which will say how many physical disks are in the array group.

  4. #4
    Join Date
    Jan 2003
    Posts
    1,605
    Hi,
    thanks to you all guys.

    Azs0309, on web site: http://publib.boulder.ibm.com/infoce...n/t0004987.htm
    there is statement: "In earlier versions of DB2 UDB, the DB2_STRIPED_CONTAINERS registry variable was used to create table spaces with an extent sized tag. However, because this is now the default behavior, this registry variable no longer has any affect."

    Thanks,
    Grofaty
    Last edited by grofaty; 03-11-08 at 04:13.

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