Thursday, November 13, 2008

Storage System

Physical Volume: Name for an actual disk e.g SSA, SCSI disk; a PV can belong to a VG only

Volume Group: It is the largest unit of storage allocation; It contains multiple PV under a single VG name. The combined storage of all the PV makes a total space of VG which is used in turn by File Systems and Logical Volumes. A VG is splitted into PP; the size of PP within VG remains constant.

Why to create separate VG? e.g datavg and rootvg.
ans: To separate userdata from OS files; Disaster Recovery; Data portability; Data integrity and security | Maintenance is easy because you can update or reinstall OS without restoring data.
You can make VG unavailable using VARRYOFFVG.
There can be 255 VGs per System.

Physical Partition: PP is the division of PV. It is the basic unit of disk space allocation.
Default max no. of PP per PV is 1016. PP size cannot be changes dynamically but the number of PP per PV can be changed dynamically in mulitples of 1016. (i.e 1016, 2032, ...)

(Note: If you increase the more than 1016 PP per PV, then no. of PV per VG will be reduced)

Logical Volume: LV contains one or more LP within the VG. LV may span the PV if the multiple PV within the VG. LV size may be increased dynamically using SMIT even when users are working on that LV. However, the size cannot be reduced easily.

MAX PV=32 (128 BIG VG)
MAX LV=255 (512 BIG VG)
MAX VG =255 per system

Logical Partition: LP within a VG is the same size as PP

LVM does mapping between LV (logical view of storage) and PV (actual view of storage).

1 comment:

Deep Sherchan said...

Great insight...keep posting