virtualization.info

Hello Massimiliano and thank you for joining us on virtualization.info.
You are worldwide famous for your Perl script VMBK, able to perform virtual machines live backup in a VMware ESX server infrastructure.
Now you just released the first beta of a new tool, VMCL, which seems even more exciting.

VI: Can you explain what VMCL does?
MD: VMCL is the first free high availability software for VMware environment, It’s based on famous Linux-ha cluster software.
It manages virtual machines failover when a physical host crashes
VMCL has a feature actually not available in any other commercial product: it decides which available physical host has to start faulty virtual machines depending on specific parameters (free memory, CPU usage) to be respected and considering a defined priority.

The whole thing is based on a quorum disk (a VMDK formatted ext3) created for every physical host, where every virtual machine configuration file (.vmx) is copied and synchronized.

When a physical host is faulty VMCL will decide which remained physical host has to mount faulted host quorum and to start which virtual machine.

VI: To achieve such results with kind of infrastructure we’ll need in terms of networking speed and storage capacity?
MD: You need very few resource: 1 network adapter for heartbeat if you don’t use console network adapter, 100 MByte for the quorum disk on a VMFS volume for each physical host.
Anyway VMCL is a porting of Linux-HA project so you could use a lot of feature of Linux-HA, like more than 1 network adapter for heartbeat, a serial port for node communication, and usage of other resource on cluster (like virtual IP).

VI: How much data is moved between synchronized hosts in typical scenarios?
MD: You have 2 synchronization process, one is the heartbeat, this is managed by Linux-HA (you can choose between a multicast/nicest/broadcast intranodes comunication) while the other one is the .vmx synchronization between the physical host and the quorum disk. This last operation occur every 2 minutes with a cron job, so we are talking about very few bytes.

VI: As you know other companies are offering this feature for ESX Server. The last one is Vizioncore expected to release esxReplicator soon. Why did you choose to distribute this tool for free when it’s evident there is a market for it?
MD:
I used to work with Veritas Cluster for VMware ESX Server on a complex virtualization infrastructure of 72 ESX Servers and I think I have a clear idea of what a cluster software have to do and what not. I’ve encountered so many problem with Veritas that I had to rewrite all VMware scripts.
VirtualCenter integration and performances were a disaster but now, with a custom agent, it works well.

The major problem of this kind of implementation is treating a virtual machine like a proccess, which can freeze cluster resources.
So I decided to create VMCL with a different design and to distribute it for free cause I’m a consultant and I sell know-how, not products.

VI: Do you plan to offer VMCL also for the upcoming VMware Server running on Linux and Windows hosts?
MD: I’ll release a version also for VMWwre Server on Linux hosts. For Windows it’s more complicated since I would need to port the Linux-HA project and it’s very time consuming. Maybe I could accommodate it for Microsoft Clustering Services.
I also plan to release a VMCL version for upcoming ESX Server 3.0.

VI: Can you provide an eta for the final release of VMCL?
MD: In the upcoming days I’ll release the beta 2 with support for more than 2 physical hosts, featuring a new automatic setup.
I hope to finish VMCL 1.0 for middle April and show it at VMware Technical Solution Exchange (TSX) in Paris.

VI: Can we expect in near future an integration of VMBK and VMCL?
MD: I’m thinking to use Minime project library to create a graphical interface for both VMBK and VMCL.

As a scoop for virtualization.info I tell you I’m implementing a smart copy for VMBK where only modified .vmdk blocks will be transferred.