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2 Replies Latest reply: Nov 29, 2013 4:14 AM by PaulAlsemgeest RSS

Oracle ASM as a way of handling lowering disk usage

PaulAlsemgeest Newbie
Currently Being Moderated

Hi,

I'm not very into ASM. Hardly ever use it, because I always use filesystem, mostly on LVM.

 

Let me first illustrate the business case.

Now I have a requirement of a database, that needs to up & downsize. Currently, it's about 4Tb large, so total disk allocated is say, 4.5Tb. But the customer is dropping a lot of old data, so tablespaces can get smaller, datafiles smaller, and the total disk usage will become about 2Tb. We would like to be able to reduce disk size (and increase easily in the future if needed). This is because, the customer has to pay some amount each month for their disk usage.

 

My idea

If I use ASM, and define a +DATA group with say about 10 partitions of 450Gb, I have a 4.5Tb. If disk usage is smaller (due to the smaller tablespaces), I can simply remove one or two partitions, and let ASM balance. If the partitions are removed, I can use fdisk linux commands to remove them. After that, the storage engineer would be able to remove them. Hence, the disk usage is lowered. Of course, this is not daily up & down, but let's say once or twice a year. Of course, rebalancing is an intensive action, but it should work fine in these cases.

 

My questions and doubts.

  1. Is it possible to create so many disk partitions in Linux. What are the pittfalls I should look for?
  2. How to remove a disk the right way (what are all the steps needed for ASM and linux commands)?
  3. Would the storage engineer be able to identify the disk that has to be removed. How?

 

All environment (if needed) is Oracle Linux 5.7, and 11.2.0.3 EE rdbms. Your comments are greatly appreciated.

 

Paul

  • 1. Re: Oracle ASM as a way of handling lowering disk usage
    Levi-Pereira Guru
    Currently Being Moderated

    If I use ASM, and define a +DATA group with say about 10 partitions of 450Gb, I have a 4.5Tb. If disk usage is smaller (due to the smaller tablespaces), I can simply remove one or two partitions, and let ASM balance. If the partitions are removed, I can use fdisk linux commands to remove them.


    Instead 10 partition in one (1) Lun of 4.5TB, create 10 Luns of 450GB each and one partition per Lun.

    My recommendation:

    As you plan use only 2TB in the future I recommend you create LUN of 200GB each, this way you can save more space.

    Using 200GB of LUN you don't need wait free 450GB to remove the Lun. In each 200GB you can free or add more 200GB as needed.


    My questions and doubts.

    Is it possible to create so many disk partitions in Linux. What are the pittfalls I should look for?

    Answered above

     

    How to remove a disk the right way (what are all the steps needed for ASM and linux commands)?

    ASM Steps:

    Follow step in documentation.

    Administering Oracle ASM Disk Groups

     

    Linux Step:

    Answered below.

     

    Would the storage engineer be able to identify the disk that has to be removed. How?

    Skill and knowledge is needed on OS and Storage S/W.

    You will need a SA.

    I suppose you have this documented. right?

  • 2. Re: Oracle ASM as a way of handling lowering disk usage
    PaulAlsemgeest Newbie
    Currently Being Moderated

    Thanks for your comments.

    After some playing around with Virtualbox, I found out many steps. One thing remains: If I delete partition /dev/sdg1,  how can we find which disk can be removed from the host (in this case virtualbox client). I guess that is only fixable by keeping a good documentation. Right?

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