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7 Replies Latest reply: Oct 3, 2013 10:30 AM by User328666 RSS

Question about a file system storage option for RAC on 10g

user12144220 Newbie
Currently Being Moderated

Hello everyone,

 

I am in the beginning of connecting our storage and switches, and building RAC on them but there is a little argument between our specialists.

 

We have two database servers(10g with OEL 5) to be clustered and two visible disk groups to each of those nodes. So question is can we choose only one disk group as a shared storage leaving the rest one as the redundant copy during database a creation window while installing the database.  Because some of us argue that oracle database has a built-in capability to decide on what level of RAID we store our data.

 

Thank you for your help.

  • 1. Re: Question about a file system storage option for RAC on 10g
    Hemant K Chitale Oracle ACE
    Currently Being Moderated

    Are these two "disk groups"  ASM disk groups  ?   I presume not because your post title mentions "file system".  You'd need to be running a Certified Cluster File System if you want to run NAS.

     

    The Database cannot see disk groups.  It does not have a "built-in capability to decide on what level of RAID we store our data".

     

    ASM can miror data between multiple logical volumes from storage when you setup a single ASM disk group with redundancy NORMAL.  But ASM doesn't deliver a "filesystem".  Particularly in 10g ASM is only for the database (not even for the RDBMS binaries etc).

     

     

    Hemant K Chitale


  • 2. Re: Question about a file system storage option for RAC on 10g
    Hemant K Chitale Oracle ACE
    Currently Being Moderated

    Why a 10g cluster ?  Why not 11gR2 ?

     

    10g has already exited Premier Support and is only in Sustaining Support for existing 10g users.

     

    See http://www.oracle.com/us/support/library/lifetime-support-technology-069183.pdf

     

    Hemant K Chitale

  • 3. Re: Question about a file system storage option for RAC on 10g
    user12144220 Newbie
    Currently Being Moderated

    There are two disk groups we have. We will not use ASM this time. Our main concern is now which level we should provide redundancy. Our system administrator can do replication on storage while our oracle dba can do the same at oracle database.

     

    Thank you for your help.

  • 4. Re: Question about a file system storage option for RAC on 10g
    Hemant K Chitale Oracle ACE
    Currently Being Moderated

    >our oracle dba can do the same at oracle database

    How ?

     

    With two disk groups in one storage cabinet, it is not "replication"  but "mirroring" that is done.  "replication" is done to another storage cabinet in a different building / DR site.

     

    Have you addressed the requirement of a Certified Cluster File System for RAC ?

     

    Hemant K Chitale

  • 5. Re: Question about a file system storage option for RAC on 10g
    user12144220 Newbie
    Currently Being Moderated

    I have seen a Certified Cluster File System for RAC before.

     

    Today, one of DBAs who has a contract with us said it is fully possible to mirror those two separate disk groups during database creation(in the wizard window). We don't want the replication mentioned above because it can be done at the storage level and it can't provide any redundancy.

     

    So only option we have now is how do we make those two disk groups a single instance and use it as a shared storage? Is it possible?

     

    Thank you for your help.

  • 6. Re: Question about a file system storage option for RAC on 10g
    Hemant K Chitale Oracle ACE
    Currently Being Moderated

    >it is fully possible to mirror those two separate disk groups during database creation(in the wizard window).

     

    I have NO idea what he means by that.  Ask him again.   It would be possible if you are combining them using ASM -- not as filesystem.

     

     

    Hemant K Chitale

  • 7. Re: Question about a file system storage option for RAC on 10g
    User328666 Newbie
    Currently Being Moderated

    "some of us argue that oracle database has a built-in capability to decide on what level of RAID we store our data". 

    That statement is not true.  Oracle has optional multiplexing for control files, redo logs, and archive logs but this is not enabled by default and Oracle will not automatically enable it.  If you want redundancy of tables, indexes, temp, and undo you must provide this because Oracle does not offer it standard or as an option.  You can achieve redundancy with RAID at the array level, or host based mirroring (like ASM redundancy groups or Linux mdadm).  This can also depend on your file system because, I think, OCFS2 does not support host based mirroring (so you cannot use mdadm or lvm to mirror the storage if you are using OCFS2).

     

    Redundancy is not required, but it is recommended if you are using hard disks because they are prone to failures.  You can configure RAID 10 across all disks in the array and present this as one big LUN to the database server.  If you have two storage arrays and you want to mirror the data across the two arrays, then present all of the devices as JBOD and use Linux mdadm to create your RAID group.

     

    RAC requires shared storage.  Maybe you have a NAS or SAN device, and you will present LUNs to the Oracle database servers.  That is no problem.  The problem is making those LUNs usable by Oracle RAC.  When I used Oracle 10g RAC, I used the Linux raw device facility to manage these LUNs and make them ready for Oracle RAC.  However, raw has been desupported.  Today I would use either ASM or OCFS2.  This has nothing to do with redundancy, this is just because you are using RAC.

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