Share data between a physical server and Integrity Virtual Machine

[Tricia Sambrano]

I would like to temporarily be able to move access to my data on an Integrity Virtual Machine (v4.3) to a physical server. The data, however, is presented using both lvols and disk devices from the IVM host. And I need to be able to switch back to the IVM Guest after a couple of days.

I need to minimize downtime and impact to the end users. If this were all disk devices, it would be easy, but the vg/lvol presentation is throwing me. Any advice?

IVM Host: HP-UX 11.31
IVM Guest: HP-UX 11.23
Physical Server: HP-UX 11.31

Thanks,
Trish

[Bill Hassell]

A virtual machine is a separate computer system with its own OS and filesystems. Use NFS to share the data just like separate computer boxes.

[Tricia Sambrano]

Bill,

I apologize. I wasn't clear- let me try again.

The situation:
We have an HP-UX 11.23 IVM guest that we would like to upgrade to 11.31. However, the client would like to minimize the downtime to the end users (developers). They also have a currently unused 11.31 server.

The idea (assuming lots of backups steps in between):
1. Allocate SAN space, create on the physical server the same data LVM structure as on the VM, and restore the dev data from the weekend cold backup.
2. Allow the DBA, and a couple of developers to test on the physical server (this is using the weekend restore).
3. If all is tested good, unmount (vgchange)the restore copy, then somehow move the vgs from the VM to the physical server (re-verify) and have the developers work there while we upgrade the VM to 11.31 (now using the restore copy of the data).
4. Upgrade the VM to 11.31, test, then switch the real data back to the VM, test, then release to developers.

I am thinking of this as a pseudo- SG active-passive scenario. This would be easy if it were for the fact that the guest was allocated LVs and disk devices.

Thanks for the help.
Trish

[Eric SAUBIGNAC]

Bonjour Trish,

There is no problem to exchange VG between a physical host and a virtual machine, as long as physical disks are presented ASIS to a virtual machine.

For example, just vgexport the source VG on the physical box (to prevent simultaneous activation on several hosts), then present the disks to the VM host, identify the disks, attach them to the VM Guest, boot the guest then finally import the VG in the guests'os. The scenario is about the same than between 2 physical boxes : the only difference is that you must bind the disks to the guest.

If the virtual guest's disks don't rely on physical disks, I mean logical volumes or files are used as backing store for the guest, you will not be able to exchange VG between a pysical box and a virtual one. For example, if you a present a LV to a virtual machine, then the guest will see it as a virtual disk. After, you are supposed to create in the guest a VG on this virtual disk. Conclusion : an LVM structure over an LVM structure ... that you will not be able to handle in a single pysical host.

Just be aware that LVM and filesystems versions must be compatible between the 2 hosts. For exemple if you work with LVM 2.1 in a given 11.31 host (whatever physical or virtual it is) you will not be able to import them in a 11.23 host (whatever physical or virtual it is)

Eric

Eric

[Tricia Sambrano]

Merci Eric,

I had pretty much come to the same conclusion. Luckily, the client is amenable to having to restore the data as the backing store presented to the guest is a mix of virtual lvdisks and virtual disks (too much administrator turnover).

I am using the opportunity to rebuild the guest's io so as to take advantage of the agile devices on the host.

Thanks,
Trish

[Eric SAUBIGNAC]

"a mix of virtual lvdisks and virtual disks"

There is a chance, a little one, that it could work with LV as backing store : if the virtual devices are used by the VM directly as filesystems. In other words if they are not under LVM control. Thats means that you mount directly /dev/disk/diskxxx in the guest.

In this case, instead of :

Host disk --> Host LV --> Guest Disk --> Guest LV --> Guest FS

you have :

Host Disk --> Host LV --> Guest Disk --> Guest FS

In this case and only in this case you can move data between a host and a guest. In all others cases you must copy the data.

Eric

[Tricia Sambrano]

That would be an interesting exercise to try (will have to play with that on my sandbox when I get some time).

Regretfully, this is a situation where the volume group on the guest contains both lvdisk and disk so I don't see a way of doing this.

At this point, I am actually glad because now I have a good reason to redo the io to the guest and use the agile devices which gets rid of the extra LVM layer from the host.

Thanks for the idea,
Trish