How is storage configured for a Virtual/Virtual Cluster?

[John McNulty_2]

My problem is how to configure storage in an Integrity VM Virtual/Virtual Cluster, as defined in the "Designing High Availability Solutions with ServiceGuard and Integrity VM" guide, and the "HP Integrity Virtual Machines Installation, Configuration, and Administration" guide.

First of all, this configuration consists of 2 x rx6600s with an EVA 4000 providing SAN storage to both. We need multi path support, so LVM PVlinks on each of the rx6600s is the usual supported solution.

Normally an SG cluster controls LVM VGs and when a package moves from one node to another, the VGs move with it.

But in Integrity VMs you're not allowed to LVM at the VM level to do multi-pathing, it has to be done on the VM host. The documentation is quite clear about this.

So, if I have to use LVM on the VM Hosts, then present LVs to the VM Guests (as Virtual LvDisks) then they appear on the VM Guests as regular disks, no LVM involved.

Next I move onto combining the VM Guests into an SG cluster. But now I have a problem. How is ServiceGuard on the VMs going to control LVM access to the storage when it has no visibility of LVM on the rx6600 VM Host systems?

How on earth is this supposed to work? The documentation is strangely silent about this.

NB: I can't use HP-UX V3 because it doesn't have the security certifications needed for this customer yet.

[Torsten.]

Hi,

do you want to run the guest as a SG package or do you want to run serviceguard on the guest?

"So, if I have to use LVM on the VM Hosts, then present LVs to the VM Guests (as Virtual LvDisks) then they appear on the VM Guests as regular disks, no LVM involved."

The LVM on the host controls the "real" disk, presented as a LVOL to the guest as a virtual disk.

The LVM on the guest controls this device as its own disk - LVM is involved!

The only difference:
The guest has no alternative pathes.

[Torsten. · Accepted solution]

Another important fact:

"To use Serviceguard in Guest configurations, the backing storage
units must be whole disks. Integrity VM does not support using other types of backing stores on
primary and alternate nodes for applications that are configured as Serviceguard packages."

(Admin Guide - page 115)

So you cannot use LVM on the Host if serviceguard is running on the guest.

In this case you have to use another multipath software (e.g. securepath) on the host.

[John McNulty_2]

Hi Torsten

We want to run ServiceGuard on the Guest.

The objective of the exercise is to use VMs to replicate a dual live Campus Cluster which consists of 2 x rx6600 in a rack on one site and the same on the other site.

The top two systems in the racks are in one cluster, and the bottom two systems are in another cluster. So for the development/test environments we want to build the same configuration using VMS.

You can see what I mean if you look at Figure 8 (on page 10) in the "Designing High Availability Solutions with ServiceGuard and Integrity VM" Guide.

The "Before Consolidation" systems are how the Production systems are configured. The "After Consolidation" systems are what we want to do for Dev/Test.

[Torsten.]

I guess my second post answers the question:

"the backing storage units must be whole disks"

[John McNulty_2]

"I guess my second post answers the question:"

So now we all we have to do is chat to the customer and decide on whether to use SecurePath, or go with 2 x "cluster in a box", where we can use hpvmdevmgmt to mark the VM Host LVM LVs as shared.

Thanks for clearing that up and helping out. The documentation needs to be a bit clearer about what's going on here.

[Thomas J. Harrold]

Interesting topic. I was involved in Beta testing of IVM 2, and I can't speak to the "official" supportability, but I was able to use LVM to present disk to IVMs, and setup MC/SG within the guests.

I'm scratching my head, trying to figure out why this would present a support issue for HP..

I hope to do some testing with IVM3 soon, so I may test this again...

-tjh

[Torsten.]

IMHO running 2 cluster members as guests on a single host is a bad option.

So your choice is to use a multipath software until VM is released for 11.31 - this could take a while.

From my point of view the reason for not supporting host based LVM volumes as virtual disks is simple:

How to tell the host to release the VG if the guest (as a cluster node) dies?


The guest will release "his" VG, but the host will not.

To describe what we are talking about (the not supported configuration for guests as cluster members):

The host owns disks, configured as a volume group and logical volumes. The LVOLs are assigned to a guest as virtual disks.
Now it is getting more complex - the guest is using the LVOL of the host as a virtual disk and creates an own VG and even LVOLs on it.

[Thomas J. Harrold]

I see, and that makes perfect sense. The obvious solution would be to incorporate some very basic multipathing in IVM. (please HP, don't make us pay for securepath, or some other product)

In my case, I was testing with both IVMs (each an MC/SG member) on the same physical host, so the LVM ownership issue was NOT a problem. In an ideal world, I would want to have each SG member on a separate host. If John's environment is just "test", and there is not a huge HA concern, it may be OK to leave both MC/SG members on the same host.

-tjh

[Torsten.]

You are right, with running both cluster members on the same host the VG ownership of the host is not a problem. The virtual disk has only to be shared between the guests.

The other option is to run service guard on the host and put the guest into a package.

Doing this the host will do the multipathing with pvlinks just fine.

[Thomas J. Harrold]

In many cases, ours included, we'd like to mimic a production environment by having MC/SG installed, so we can verify interaction with our SW. (we have seen RARE occasions where SW works differently inside of MC/SG - usually due to poor/old coding techniques)

I believe there is value in this approach. As long as HA is not a concern!

-tjh

[John McNulty_2]

We're doing this to create a Dev/Test solution in a single rack that reflects a production environment consisting of 4 x rx6600's split into two SG clusters. So it doesn't have to be as resilient as it would if it were a proper production solution.

In the end we've decided to IVM cluster across both systems, and use SecurePath as recommended.

Thanks again.