Business Copy EVA Question

[CDI Support]

Hi

I have completed my backup after creating a snapshot and mounting it on the backup host. Now I am ready to unmount it and un-present it from the host so that I can delete the snapshot and recreate it (to refresh). what guarantees me that I will see the same device from an HP-UX host.I am trying to perform everything through SSSU and I am not clear on this. Am I missing any step in between to make sure that I am getting the same device for the snapshot? Can some one please explain me?

Thank You
Sundar R

[Bill Costigan · Accepted solution]

If you use the same LUN number you should get the same device file. I would keep the time when there is no snapshot to a minimum. When the LUN is gone, an ioscan will show NO H/W. If the system is rebooted during this time, the device files may go away and be rebuilt with another channel number.

I would do the following together in a script:
unmount each filesystems using the snapshot
vgchange -a n /dev/vg20 (assuming this is the volume group with the EVA LUNS)
use SSSU to remove and recreate the LUNs using the same LUN numbers.
vgchange -a y /dev/vg20
remount the filesystems

Note: the filename has three numbers:
cXXtYYdZZ
The YYs and ZZs are based on the LUN number
LUN# = 8*YY + ZZ
the XX is assigned to each unique hardware path. The hardware path is made up of the internal bus path to the fiber card and the Fabric port ID assigned to the EVA controller port by the SAN switch.

You might be able to preserve the XX number by ensuring that there will always be a LUN visible on that path. e.g, create a 10MB LUN and assign it to the host. It will show up in ioscan but not be used.

[CDI Support]

Hi

Thank you . In the sequence you have given, dont we have to include vgexport and vgimport .

unmount each filesystems using the snapshot
vgchange -a n /dev/vg20 (assuming this is
the volume group with the EVA LUNS)
**** vgexport with -s option ***
use SSSU/ GUI to remove and recreate the LUNs using the same LUN numbers.
*** vgimport ***
vgchange -a y /dev/vg20
remount the filesystems


Thank You
Sundar R

[Bill Costigan]

No you only have to do a vgexport and vgimport if the device files are changing.

vgchange -a n tells LVM to stop using the disks and vgchange -a y forces LVM to go out and reread the disks and update its internal tables.

As long as the number of disks and the device names stay the same there is no need to reload the /etc/lvmtab file which is what the vgimport will do.

If you do the vgexport it will remove the /dev/vgxx/group file and all the associated directories and device files. You would then have to remake the /dev/vg00/group file with the correct major and minor numbers. Just more work.

Of course if the device files did change and you didn't know what the new names were then the vgimport with the -s would search all the disks on the system looking for the disks that made up that volume group.

If you add disks or lvols you'll have to go through a vgimport. I did forget to mention that you should also do an fsck on each of the raw lvols before duing the mounts.

[CDI Support]

Hi

I have one more question. When I create the snapshot using "add snapshot" , I don't see the option to specify the LUN #. I have such option only when I create the storage using "add storage".

How do specify the LUN# when I create the snapshot !! Is there any workaround ? Can someone please post the command synatx if you have ?

Thank You
Sundar R

[Bill Costigan]

That would be the ADD LUN command

ADD LUN 34 VDISK="\Virtual Disks\disk4\copy2" HOSTS=\hosts\hpuxhost2

[CDI Support]

Hi

As per the Storage System scripting Utlity manual I have to use the delete storage to remove a snapshot.In order to refresh the snapshot.

Can someone please confirm/correct the sequence below

1.Delete the storage using

DELETE STORAGE \Virtual Disks\payroll_backup

2.Create the snapshot

ADD SNAPSHOT \Virtual Disks\payroll_backup STORAGE=\Virtual
Disks\payroll\ACTIVE ALLOCATION_POLICY=DEMAND

3. Add the LUN ?

ADD LUN 34 VDISK=\Virtual Disks\payroll_backup HOSTS=\hosts\hpuxhost2

Thank You