EMC: Using split BCVs

Title:

EMC: Using split BCVs

Author:

Douglas O’Leary <dkoleary@olearycomputers.com>

Description:

EMC: Using split BCVs

Date created:

06/2001

Date updated:

07/2005

Disclaimer:

Standard: Use the information that follows at your own risk. If you screw up a system, don’t blame it on me…

So, you’ve managed to get your Timefinder software working correctly (at least, you think you have), and you’ve split off the BCVs; now, you want to use the BCVs as a backup or as a testbed. Either way, you have some issues - particularly if you want to use the BCVs on the same host as the standard device.

The issue revolves around the volume or disk group header information. Conceptually, this is the same for both Veritas Volume manager and HP’s Logical Volume Manager. Both volume managers store information about the volume/disk group on the disks that comprise the group. So, when you split off the BCVs, the information encoded there is the exact same as the information on the standard devices. There won’t be a separate volume/disk group, LV/volume to mount because everything thinks its the same thing.

So, you have to figure a way around that. Fortunately, there’s a way for both HP’s Logical volume manager and Veritas’ Volume manager. To wit:

HP Logical volume manager - vgchgid

  • Split the BCV’s from the Symmetrix disk group. For the sake of this example, assume the BCV disks are as follows::

    /dev/dsk/c2t0d0
/dev/dsk/c2t1d0
/dev/dsk/c3t0d0
/dev/dsk/c3t1d0

  • Create an array with the appropriate disk names. Creating an array is optional; however, it’ll really help prevent typos which, in this case, could keep your system running longer.

    set -A bcvs /dev/dsk/c2t0d0 /dev/dsk/c2t1d0 /dev/dsk/c3t0d0 \
/dev/dsk/c3t1d0

  • Create an vgexport map file for the volume group - particularly if you’re using nonstandard logical volume names.

    vgexport -p -m /tmp/${vg}.map

  • Create the new volume group directory structure as needed:

    mkdir /dev/vgbcv
mknod /dev/vgbcv/group c 64 0x0#0000

  • Change the volume group header information on all the BCV disks simultaneously:

    /usr/sbin/vgchgid ${bcvs[*]}

  • Import the new volume group:

    vgimport -m /tmp/${vg}.map vgbcv ${bcvs[*]}

  • Mount the filesystems and do with them as you will.

Veritas Volume Manager

Need procedures for vxvm

Oracle considerations

Similar in vein to the various volume managers, you can’t have two instances of the same database running simultaneously. Therefore, you have to convince the database on the BCVs that it’s actually working as a different SID. Once I figure out what the procedures for that is, I’ll be posting them here.