VMware vsphere 5.1 cluster detailed (11) vmotion and eVC

Part II vsphere DRS (distributed resource Scheduling)

Chapter II Vmotion and EVC

Vmotion may be one of the best examples of functional change in the industry, when virtualization is first launched, all about the flexibility and portability of virtual machines, however, portability and flexibility are restricted when the virtual machine is powered on, and when VMware introduces Vmotion, introduces them to change the world's it, Vmotion is literally a development on an existing component, based on the "Pause and restore" feature, so don't misread the last sentence, but Vmotion is really a brilliant technique.

As you would expect, Vmotion is a feature that, when turned on, allows you to migrate a virtual machine from one host to another without shutting down the virtual machine, but the question remains, how does it work? This is a rather complicated process, this point has been optimized for years, allowing you to perform 8 concurrent vmotion on a host that supports a 10GB network, and in writing this article, limit the concurrency of 4 vmotion to a host that supports a 1GB network.

What is a vmotion workflow?

1. Verify target host Compatibility

2. Create a copy of the virtual machine on the target host

3. Copy each memory page from the source address to the destination address via a vmotion network called Pre-replication

4. Perform the memory of the replicated virtual machine on the target virtual machine, and then copy the memory pages generated in the pre-replication process

5. Continue to replicate the memory pages during the last copy until it's not changed

6. "Stun" the source virtual machine to restore status on the target virtual machine.

It sounds very simple, is it true, there are only 6 steps? However, there are also some problems, such as the change in the amount of memory over the Vmotion network throughput, we do not want to know what happens under such scenarios, for example, the database server has very large active memory.

In Vsphere 4.1, VMware introduced some of the features of vmotion-fast recovery, fast recovery on, and the source virtual opportunity being "dizzy", where all the pages were replicated and the virtual machines were opened on the target host. However, the virtual machine is already running on the target host, and when it is not fully replicated, it may try to read or write this page, in which case the rapid deployment will get the request page from the source and allow the client to complete the requested operation while continuing to replicate the remaining memory pages, knowing that all the pages are migrated, What happens if a vmotion network fails?

The destination virtual machine cannot enter the memory page. Because they are "live" remote, vsphere 4.1, in order to solve this situation, use the security mechanism of storage to implement fault, that is to say, will create a special file, this file is basically used as backup buffer, in case of network failure, Is it cool to allow this file to complete the migration and provide two-way communication between the two hosts?

A typical problem will arise, whether this will affect performance. Well, it's understandable that without fast recovery, Vmotion's large active memory virtual machines will be very difficult to switch over for a long time and may result in loss of connectivity to the virtual machine, although rapid recovery can affect page access, but it has great benefits for virtual machines when not replicated. While the temporary increase in memory access time impact is negligible, vsphere 5.0, rapid recovery is eliminated, will introduce new features to everyone, let's see what has changed.

Vmotion's change?

In Vsphere 5.0, when it comes to scalability and performance, the fundamentals of vmotion change.

Vmotion multiple NIC Support

"Vertigo" When the page is sent

Support for high link latency

Improve Error Reporting

Vmotion multiple NIC Support

We're going to talk about a very essential and vmotion feature that vmotion can now work with multiple Web cards to reduce vmotion operating time, meaning that even a single vmotion could take advantage of all the configured Vmotion network adapters. Vsphere 5.0, only one NIC is used to enable vmotion,vmotion the use of multiple network adapters will require the removal of some bandwidth and throughput constraints, the following list shows the current maximum number of network adapter Vmotion support:

1gbe– supports 16 network adapters

10gbe-supports 4 network adapters

Important to achieve Gigabit Ethernet access, the server to configure the latest PCI card to use the million gigabit bandwidth, this requirement

To ensure that your server is able to take full advantage of these capabilities.

Basic design Principles

When designing your virtualized environment, where you design your network architecture, you need to consider the specification of the virtual machine, and if you have enough bandwidth for vmotion, the migration completes faster, and the virtual machine leaves the host earlier. When designing a server platform, you need to consider peak network bandwidth-not just the ability to consider the network card, but also the ability of the PCI bus.