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  1. #1
    Join Date
    Jan 2010
    Posts
    67

    Unanswered: db2 database layout on SAN

    Hi There;

    we are going to upgrade our databases (5 databses and the largest is 200 GB) from v7.2 to 9.7 in new server.

    in new server we will use SAN (one LUN for server with 36 disks under AIX 6.1).

    I am going to build the database from scratch and I need your advise.

    1- is it necessary in new environment(using SAN) I create separate filesystems for each database (as it is in old server) ?

    2- I thought:
    /db/data data filesystem for all databases,
    /db/ind index filesystem for all dataabse
    /db/tmp
    /db/activelog
    /db/archivelog

    really appreciate if give me your comments on this

  2. #2
    Join Date
    Apr 2006
    Location
    Belgium
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    Provided Answers: 11
    it really depends how much administration you want from system team
    usually I request (depending on the size)
    x /db/data1 /db/data2 ... data filesystem for all databases,
    x /db/ind index filesystem for all database
    some customers even have x fs by db for data and index
    /db/activelog
    /db/archivelog
    /db/diaglog
    /db/config
    Best Regards, Guy Przytula
    Database Software Consultant
    Good DBAs are not formed in a week or a month. They are created little by little, day by day. Protracted and patient effort is needed to develop good DBAs.
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  3. #3
    Join Date
    Jan 2010
    Posts
    67
    Thank you Przytula for your response.

    my question is from performance point of view, is it really need we create separate filesystems ? SAN will stripe by itself, if you agree with my second question is what is disadvantage with the layout I mentioned before

    thank you again for your help

  4. #4
    Join Date
    Jun 2003
    Location
    Toronto, Canada
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    Provided Answers: 1
    If it's just one LUN RAID10-ed over 36 disks, it does not matter from the performance point of view if you have separate file systems or just one big pile of junk. Separate file systems might be preferential from the maintenance perspective but, since you're asking this, you probably wouldn't care.

    For better performance you want to use separate physical device for each database and each set of active logs.
    ---
    "It does not work" is not a valid problem statement.

  5. #5
    Join Date
    Jan 2010
    Posts
    67
    Hi n_i

    it is one LUN RAID 5 with 36 DISK,

    I agree with you from performance point of view separate filesystems has no difference in SAN environment but from independent security failure may be it is matter for example if I put all activelog databases under one filesystem /db/activelog and in massive deletion of one database the filesystem become full it will impact all databases. please correct me if I am wrong? how we can consider this ?

  6. #6
    Join Date
    Jun 2003
    Location
    Toronto, Canada
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    Provided Answers: 1
    Quote Originally Posted by mars View Post

    it is one LUN RAID 5 with 36 DISK,
    It is a bad idea to use RAID5 for logs.
    ---
    "It does not work" is not a valid problem statement.

  7. #7
    Join Date
    Aug 2008
    Location
    Toronto, Canada
    Posts
    2,367
    Quote Originally Posted by mars View Post

    if I put all activelog databases under one filesystem /db/activelog and in massive deletion of one database the filesystem become full it will impact all databases.

    Size /db/activelog large enough to store (logprimary + logsecond) x (# of db).

  8. #8
    Join Date
    Jan 2010
    Posts
    67
    Hi All,

    Thank you all for your help and information.

    but I think you did not get my question.

    I am trying to find out what should be the database layout on SAN system compare with local disk from point of performance and saving space let me I ask my question like this:

    1- do you think still I need different filesystems for every database in server or we can assume SAN will striping the all on its disks under LUN?
    e.g: /db/db1/data
    /db/db1/ind
    /db/db1/log
    .
    .
    .
    /db/db5/data
    /db/db5/ind
    ...

    OR JUST

    /db/alldb/data
    /db/alldb/ind
    /db/alldb/log
    .
    .
    .
    .

    what is advantage and disadvantage the second type of layout from performance and security (if one filesystem fail will impact to all DBs) on SAN .

    Thank you in advance for your help.

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