Cluster Filesystem for Hyper-V

ToddMuirhead — Tue, 17 Jun 2008 22:04:00 GMT

I ran across Scott Lowe's blog entry on Melio FS, Hyper-V, and VMware ESX earlier today. Scott talks about his discussion with Jeff Woolsey - Senior Program Manager for Virtualziation at Microsoft - while at Tech Ed. Specifically how Microsoft has allowed storage partners to create a cluster file system that can be used by Windows 2008 \ Hyper-V. Such a cluster file system could enable the VMFS type functionality of having multiple physical hosts access a shared disk at the same time. This would remove the requirement of one LUN for one VM when doing quick migration with Hyper-V. Specifically Sanbolics' Melio FS was identified as capable of doing this.

I think this is excellent news and means that Hyper-V customers will have a cluster file system option for their Hyper-V hosts. This can greatly simplify storage management when you have more than just a few VMs. On the downside is the additional cost of such a cluster file system. There is not pricing listed on the Sanbolic website, but the Network World article states that the price is $5000 per host. If the cost is anywhere near that, then the price of VMware's ESX doesn't seem that bad in comparison to Hyper-V - assuming that you need or want the cluster file system capability.

Todd

Hyper-V Quick Migration Part II

ToddMuirhead — Fri, 18 Apr 2008 22:15:00 GMT

The second post on the Microsoft Virtualzation Team Blog about Quick Migration and VMotion was added a few days ago. It is mostly a discussion about how VMware HA and Quick Migration both provide a failover solution for UNplanned downtime. I agree with Jeff that both do basically the same thing in the event of an unplanned server outage - the VM is moved to another server and restarted.

The difference that he doesn't talk about is that the rules of the failover are different because of the underlying filesystem that is used in each solution. Microsoft Hyper-V and Quick Migration are using the tried and true Microsoft failover-clustering, which uses an NTFS filesystem on the shared storage. As this is not a cluster file system, the shared storage is actually only visible to one of the servers at a time to prevent corruption. VMware ESX server and VMware HA are working with VMs that are on a VMFS file system which is cluster aware - meaning that multiple ESX servers are able to access the files (or VMs in other words) at the same time.

So following a failure of a Hyper-V server, all VMs on the same disk (or LUN) must be recovered on the same server because the LUN or disk can only be used by one server at a time. In the event of a failure of an ESX server, the VMs can be restarted on any ESX server that has access to the LUN. In order to achieve this flexibility with Hyper-V and Quick Migration it would be necessary to have each VM on it's own LUN. This isn't impossible, but could be more complex to setup and manage.

The end result would be same - the VMs would be restarted on another server. Some of the underlying details can make a difference with flexibility in where those VMs end up.

Todd

Virtualization Frontier

Cluster Filesystem for Hyper-V

Hyper-V Quick Migration Part II