Moving data from old SAN to new SAN

[Debbie Beresford]

We have purchased a new SAN and I need to move the data from our old san to the new one.  The layout and sizes of the volume groups and logical volumes will remain the same. 

Since everything is the same with the exception of the physical disks, I am thinking I should be able to add the new disks as alternate disks using vgextend.  I can then remove the original disks with vgreduce and the data will apear on the new disks.  Does this seem logical?  If so, can someone help with the proper syntax.

The other two options I was thinking of involved vgexport/vgimport or restoring from tape. 

Any help with the easiest way to do this would be greatly appreciated.

[Patrick Wallek · Accepted solution]

Comments on your ideas:

>> I am thinking I should be able to add the new disks as alternate disks using vgextend.  I can then remove the original

>>disks with vgreduce and the data will apear on the new disks.  Does this seem logical?

Unfortunately, no.  When  you add a new disk to a volume group, you cannot specify that it is an alternate path.  LVM will determine if a new disk is an alternate path for an existing disk.  Soo when you would a disk from the new array it would just show up in the VG as a new disk ready to be used.

Also, data will not just magically "apear on the new disks."  Data has to be put there somehow.

>>The other two options I was thinking of involved vgexport/vgimport

vgexport / vgimport would not help you in this instance either.  vgimporting a VG requires that there be VG structures on the disks that you are importing.  In the case of the new disk array nothing would be there, so there's nothing to import.

>>or restoring from tape. 

That would be an option, but you would have to create your VGs and LVs from scratch with LUNs from the new disk array.  Depending on the number of VGs and LVs, this could take a while.  As far as data restoration goes, that could take quite a while depending on the amount of data and type type of backup device you are using.

Here's how I would migrate data between disk arrays:

1. Create LUNs on the new disk array
2. Present them to the HP-UX server
3. Add the LUNs into the appropriate volume groups (pvcreate, vgextend)
4. Using LVM mirroring to mirror the data from the current LUNs to the new LUNs (lvextend -m 1)
5. Verify that the data has been successfully mirrored (vgdisplay, lvdisplay)
6. Reduce the mirrors from the old LUNs (lvreduce -m 0)
7. Reduce the old LUNs out of the VG (vgreduce)
8. Repeat as needed for each VG

[Debbie Beresford]

Reading the documention on lvextend, additional software is required to do the mirroring.  I believe we have this:

/usr/sbin/swlist -l bundle | grep -i mirror
  B2491BA               B.11.23        MirrorDisk/UX (Server)

Is this the correct software? 

[Patrick Wallek]

Yes, that is the correct software.

[Debbie Beresford]

Fantastic.  This is the approach I will take.  Thank you very much for your help!