Forum Discussion

Kanag's avatar
Kanag
Level 2
15 years ago

where diskgroup details will stored if 100 disks avail on a diskgroup

Hi Gurus,


Veritas volume:

Assuming one diskgroup, there are 100 disks are added,on which disk will hold the diskgroup details(configuration)....is it all disks hold diskgroup config?

Thanks
Kanag
business continuity
Case Study
Configuring
Storage Foundation
  • Gaurav_S's avatar
    Gaurav_S
    15 years ago

    Hello Kanag,

    By default it is not stored on all the disks ..... Volume Manager will pick randomly some disks & place configuration on it....

    You can put a tunable "nconfig=<config-copies>" while initializing the diskgroup  using vxdg command.... with this parameter you can set no. of diskgroup copies you want...

    # vxdg list <diskgroup>  |grep "clean online"

    above command will display which disks holds the configuration...




    From the man page of vxdg command


    The nconfig and nlog operands can be used to configure the number of configuration database copies and kernel log copies that are maintained for a disk group. The config-copies and log-copies values are either a decimal number (including 0 or -1) or set to all or default. A value of all or -1 signifies that all configuration or log copies on all disks in the disk group will be maintained. A value of default or 0 (this is also the default value) signifies that the Volume Manager will manage copies that are distributed in a reasonable pattern throughout the disks and controllers on the system. Any other number signifies that a particular number of copies should be maintained (or all copies, if that number is larger than the number of available configuration or log copies on all disks).

     

    When a specific number (or default) is requested, configuration copies are scattered approximately evenly through the disk controllers on the system. If SCSI disks with multiple disks per target are found, then each such target is treated similarly to a controller (i.e., configuration copies are evenly distributed between such targets). With the default policy, one configuration or log copy is maintained for each controller, and one configuration or log copy is also maintained for each SCSI target that has multiple disks; if this does not result in allocating at least 4 copies, then additional copies are spread through the controllers and targets.

    Gaurav

  • Gaurav_S's avatar
    Gaurav_S
    Moderator
    15 years ago

    Hello Kanag,

    By default it is not stored on all the disks ..... Volume Manager will pick randomly some disks & place configuration on it....

    You can put a tunable "nconfig=<config-copies>" while initializing the diskgroup  using vxdg command.... with this parameter you can set no. of diskgroup copies you want...

    # vxdg list <diskgroup>  |grep "clean online"

    above command will display which disks holds the configuration...




    From the man page of vxdg command


    The nconfig and nlog operands can be used to configure the number of configuration database copies and kernel log copies that are maintained for a disk group. The config-copies and log-copies values are either a decimal number (including 0 or -1) or set to all or default. A value of all or -1 signifies that all configuration or log copies on all disks in the disk group will be maintained. A value of default or 0 (this is also the default value) signifies that the Volume Manager will manage copies that are distributed in a reasonable pattern throughout the disks and controllers on the system. Any other number signifies that a particular number of copies should be maintained (or all copies, if that number is larger than the number of available configuration or log copies on all disks).

     

    When a specific number (or default) is requested, configuration copies are scattered approximately evenly through the disk controllers on the system. If SCSI disks with multiple disks per target are found, then each such target is treated similarly to a controller (i.e., configuration copies are evenly distributed between such targets). With the default policy, one configuration or log copy is maintained for each controller, and one configuration or log copy is also maintained for each SCSI target that has multiple disks; if this does not result in allocating at least 4 copies, then additional copies are spread through the controllers and targets.

    Gaurav

  • Kanag's avatar
    Kanag
    Level 2
    15 years ago
    Thanks Gaurav,

    How to take diskgroup configuration backup,,,I want to restore the configuration backup,when the server OS got crashed and reinstalled os,,,,veritas diskgroup was created by SAN disks,Now all SAN disks are present,but Veritas software newly installed,is it will sense that disks are CDDISK or Sliced or hpdisk whatever.....we can directly import diskgroup from disks(if we know the disks details),,,to get data,,without restore data from backup....need to get old LV's as it is with data
  • Gaurav_S's avatar
    Gaurav_S
    Moderator
    15 years ago
    Hi Kanag,

    seems to be a different question so should go in a separate post ....  however..

    Whenever there is a configuration change, vxconfigbackupd will automatically take a backup of config .... you can use the same daemon to take manual backup ....

    If you say OS got crashed  & veritas is newly installed... it may or may not sense the disk type automatically ... You might need to reinitialize disks in Veritas again but this is a very careful step as you need to initialize the disks very carefully using correct offset values else you may not get the data...

    There would be so many methods to recover a diskgroup ... one of them is defined here:

    http://seer.entsupport.symantec.com/docs/247723.htm

    Or using vxconfigrestore

    http://sfdoccentral.symantec.com/sf/5.0/solaris/manpages/vxvm/vxconfigrestore_1m.html


    Gaurav
  • rregunta's avatar
    rregunta
    Level 4
    15 years ago
    Hello Kanag,

    If the OS and Veritas Volume Manager is reinstalled on any box and Luns (storage disks) mapped to the server had diskgroup created over them earlier, in that case Vxvm will detect the disks as they were formatted earlier under vxvm (i.e. sliced / cdsdisk etc). Vxvm will even detect the diskgroup as in deported state. But you may or may not be able to import the diskgroup due various reasons. 

    In such cases, you would need recreate the diskgroup manually or with the help Symantec Technical Support.

    Regards
    Rajesh