Wednesday, August 10, 2011

Virtual Objects on Veritas Volume Manager:

Virtual Objects:
1.        VMdisk
2.        Disk Group
3.        Sub-Disk
4.        Plex
5.        Volume

1.        When a disk is brought under the control of VxVM that disk is called VMDISK.
2.        Can bring the disk under VxVM by 2 methods.

a.    Initialization:
       The entire data on the disk will be overwritten, i.e., the data in the disk will be destroyed.
b.    Encapsulation:
       When a disk is brought under the control of VxVM with encapsulation, all the data (partition) in the disk will be preserved.

3.        Upto 31 characters.


1. Is a collection of volume manager disks that have been put together into a logical grouping.

2. Grouping of disk is for management purpose, such as to hold the data for a specific application or set of applications.

3. Volume manager objects CANNOT span disk groups. For eg: VOLUMES, SUB-DISKS, PLEXES and Disk must be derived from the same disk group.
 Can create additional disk group as necessary.

4. Disk group ease the use of devices in a high availability environment, because a disk group and its components can be moved as a unit from the host machine to another.


1. Volume manager disk can be divided into one or more sub-disks.
2. Is a collection of contiguous blocks that represent a specific portion of a volume manager disk, which is mapped to specific regions of physical disk.
3. Is a subsection of a disk's public region.
4. Is the smallest unit of storage in volume manager.
5. Conceptually, a sub-disk is similar to a partition.
6. Max size of a sub-disk is the size of the vxdisk.
7. Can create 4096 sub-disks/vmdisk.
8. Sub-disk cannot be shared among two plexes.


1. Volume manager uses sub-disks to build virtual objects called PLEXES
2. Is a structured or ordered collection on sub-disks from one or more vmdisk.
3. Cannot be shared by 2 volumes.
4. Maximum number of plexes per volumes is 32
5. Between 2 plexes of same volume mirroring occurs by default.
6. Can have minimum one sub-disk and maximum of 4096 sub-disks
7. 3 types of plexes
            a. Complete plex: holds a complete copy of a volume
            b. Log plex: dedicated to logging
            c. Sparse plex: 1. which is not a compelete copy of the volume
                                    2. Sparse plexes are not used in newer       
                                       versions of volume manager.
8. Can organize data on sub-disks to form a plex by using the following
            a. Concatenation
            b. Striping
            c. Mirroring
            d. Striping with parity

1. Is a collection of plexes
2. Is a virtual storage device that is used by applications in a manner similar to physical disk. Due to its virtual in nature a volume is not restricted by the physical disk size constraints that apply to physical disk.
3. Volume can be as large as the total sum of available unreserved free physical disk space
4. Minimum of plex in a volume is 1.
   Maximum of plexes in a volume is 32.
5. Size of the volume is the size of the least plex.
6. Maximum size of a volume is a size of the disk group

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