How to use Distributed Extent based striping and Mirroring in HP-UX | /etc/lvmpvg | implementation of mirroring and striping in HP-UX LVM | How to implement mirroring and striping 10 in HP-UX

1. What is the LVMPVG files used for? How is this used for Extent based Striping and mirroring? What is DEBS (Distributed Extent Based Striping)

LVMPVG file /etc/lvmpvg is a text file which can be created anytime on a system and specifies that for a given VG which are the PVs which are part of the Physical Volume groups.

A sample /etc/lvmpvg can be like this.

/etc/lvmpvg

VG /dev/vg01

PVG pvg01

/dev/dsk/c0t0d0

/dev/dsk/c0t0d1

PVG pvg02

/dev/dsk/c1t0d0

/dev/dsk/c1t0d0

The above file shows that the pvg0 in the VG vg01 come from controller c0 whereas the PVG pvg02 comes from the disks at the controller c1.

We will create an LV using the pvg01 disks and then will mirror the same with the disks in the PVG pvg02. The below is also known as distributed extent based striping.

lvcreate -n my_lvol -L 5000 -D y -s g -g pvg01 /dev/vg01

The above creates an LV of size 5000MB with name my_lvol in the VG vg01 and in the PVG pvg01 which means the disks /dev/vg01/c0t0d0 and /dev/vg01/c0t0d1 with the (-D y) which is the Round Robin distribution of the across the PVs in the PVG pvg01. Also -s g tells LVM that the LV has mirroring policy as PVG-Strict.

In the next step we mirror the LV

lvextend -m 1 /dev/vg01/my_lvol -g pvg01 /dev/vg01

Which creates the mirror of the LV to the disks in pvg01 that is the mirror goes to the disks /dev/dsk/c1t0d0 and /dev/dsk/c1t0d1 because of the PVG-strict policy which ensures that the mirrors of the PEs cannot remain in the same PVG.

The above is also called Distributed extent based striping and mirror which is an example of RAID 10. Also in case of DEBS the Stripe size as evident is equal to the size of the Physical extent.