Forum Discussion

MIG31's avatar
MIG31
Level 4
12 years ago

disk group

hallo Symantec world just curious whats the advantage of having a single disk group over multiple diskgroups in a SG

 

thanks,

MIG31

business continuity
Linux
Storage Foundation
  • Marianne's avatar
    Marianne
    12 years ago

    We normally create diskgroups according to usage. 

    For example, all disks for one Oracle instance will be added to one diskgroup.

    Therefore, an Oracle server with multiple instances will have one diskgroup for each instance.

    Diskgroups are also important when replication is introduced. All disks belonging to an application need to be in the same diskgroup to ensure consistency, especially where asyncronous replication is done.

    We recently had to convince a customer that different diskgroups for databases and logs had to be joined before replication could be enabled. 

  • stinsong's avatar
    stinsong
    Level 5
    12 years ago

    Hi mig31,

    It's hard to say advantage or disadvantage to have single disk group than multiple disk groups within a service group.

    When service group online, VCS import and enable all disk groups configured in it. Single disk group with many disks and volumes will cost more times to wait for the disk group resource online. But multiple disk groups will have multiple disk group resources online to complete service group online.

    So it depends on your requirement and specific circumstances of configuration of service group and disk groups.

  • MIG31's avatar
    MIG31
    Level 4
    12 years ago

    Thanks stinsong for the info it cleared my curiosity

    mig31

  • Marianne's avatar
    Marianne
    Level 6
    12 years ago

    We normally create diskgroups according to usage. 

    For example, all disks for one Oracle instance will be added to one diskgroup.

    Therefore, an Oracle server with multiple instances will have one diskgroup for each instance.

    Diskgroups are also important when replication is introduced. All disks belonging to an application need to be in the same diskgroup to ensure consistency, especially where asyncronous replication is done.

    We recently had to convince a customer that different diskgroups for databases and logs had to be joined before replication could be enabled. 

  • mikebounds's avatar
    mikebounds
    Level 6
    12 years ago

    I don't think there will much time difference.  I would say comparing :

    1. importing 1 diskgroup with 2 disks
    2. importing 2 diskgroups each with 1 disk 

    That 1 would be quicker, if for 2 you imported sequentially but in VCS you can import the 2 diskgroups simultenously, so then 2 would probably be marginally quicker, but I think there would probably be little in it.

    I would say the difference is logical.  If the service group contains 2 Apps, then I would place each app in its own diskgroup and this also means, if you want to split into 2 service groups in the future, then this is much easier.  If the service group only contains 1 App, then I would place the disks in 1 diskgroup, but I know customers who for Oracle, put data disks in 1 diskgroup and logs in a another to keep the 2 separate.  This is bad practice as you can keep data on separate disks in a single diskgroup, so there is no need for 2 diskgroups and if you later implement VVR then data and logs MUST be in the same diskgroup.

    Mike

  • MIG31's avatar
    MIG31
    Level 4
    12 years ago

    Thanks Marianne Van Den Berg and MikeBounds that was so informative. Every day is a learning process. I have learned alot from the symantec community

    Thanks

    mig31