Datacentre Support Reference Guides

EMC: Using split BCVs

 
 

 

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

  1. Split the BCV's from the Symmetrix disk group. For the sake of this example, assume the BCV disks are as follows:
    1. /dev/dsk/c2t0d0
    2. /dev/dsk/c2t1d0
    3. /dev/dsk/c3t0d0
    4. /dev/dsk/c3t1d0

  2. 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

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

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

  4. Create the new volume group directory structure as needed:

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

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

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

  6. Import the new volume group

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

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

Veritas Volume Manager instructions - provided by The Symantec Gurus! (With Thanks)

Steps to import the clone disk (including EMC BCVs) using VxVM 5.0 :

1) before we split the BCV device from vm240dg (as in example below), "vxdisk list" shows the clone disk in an error udid_mismatch status

DEVICE TYPE DISK GROUP STATUS

EMC0_1auto:cdsdiskEMC0_1vm240dgonline
EMC0_27auto- -errorudid_mismatch

2) then issue the following command to split the BCV device

/usr/symcli/bin/symmir -g vm240dg split DEV001

3) after we split the BCV device DEV001 from vm240dg, we need to issue "vxdctl enable" or "vxdisk scandisks" to update the configuration in order to see the clone disk is in "online udid_mismatch" state issuing "vxdctl enable" ( or "vxdisk scandisks"), and "vxdisk list" gives the following display

DEVICE TYPE DISK GROUP STATUS

EMC0_1auto:cdsdiskEMC0_1vm240dgonline
EMC0_27auto:cdsdisk- -onlineudid_mismatch

4) use the following comand to import the clone disk

vxdg -n newdg -o useclonedev=on -o updateid import vm240dg

5) issue "vxdisk list" to see the clone disk is imported

DEVICE TYPE DISK GROUP STATUS

EMC0_1auto:cdsdiskEMC0_1vm240dgonline 
EMC0_27auto:cdsdiskEMC0_1newdgonlineclone_disk

 

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. If the Oracle Guru's fancy sending the instructions I'll be glad to post them!