Deep Dive into the VMware VMotion

What is VMotion in VMware


VMotion is VMware technology which allows you to migrate your live running VM server from 1 physical server to another without any downtime, which allows you to have your server service/applications continuously available. This is very much helpful during your planned activity of your physical server without need of any downtime to the VM server which runs on that physical server which hosts these VM servers.




How does VMotion works?

When you do VMotion of VM, the entire state of VM is encapsulated by a set of files stored in shared storage. The filesystem used in VMware i.e. VMFS (VMware file system) allows multiple ESXi servers to access same set of files concurrently.


  • Than the active memory and execution state of VM is rapidly transferred over the high speed network. VMware keeps track of on going memory activity during VMotion activity.



  • Once the entire system state and memory is copied over the network to other ESXi server, VMotion suspends the VM from current host and transfers the remaining active memory activity and resumes it on the target ESXi server. This entire process takes less than 2 seconds on high speed network.


  • VM’s network is also virtualized by the underlying ESXI server which ensures VM’s network identity to be preserved. VMotion manages the virtual machine MAC address as part of the VMotion process and once the VM machines is been resumed VMotion pings the network router to make sure it is aware of the new physical location of MAC address. Since the migration of VM with VMotion preserves the precise execution state, the network state and identity and this results in zero downtime.


Hence even users who are continuously working on this VM servers doesn’t seems to see any difference even though at background it is been migrated from one physical ESXI server to another ESXi server.

So this is how VMotion works at the backend.

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How does Storage VMotion or SVMotion works in VMware vSphere 5.5

How does Storage VMotion or SVMotion works in VMware vSphere 5.5

I have seen many guys asking this question, that how does SVMotion works at background and what are the process that is happening at the backend.

Storage VMotion is really a great feature which enables you to migrate your VM’s storage or Virtual disks from one datastore to another datastore without any downtime and yes now started from vSphere 5.5  using web client, you can do both VMotion and SVMotion of powered ON virtual machines simultaneously which was not possible earlier.



So how storage VMotion works?

So when you do SVMotion, all the non-volatile files that make up a VM is been copied first to the destination datastore i.e. .VMX, swp, snapshots and log files.So how storage VMotion works?

  • It starts a shadow VM on the destination datastore, as shadow VM doesn’t have virtual disks, it sits idle waiting for its virtual disks.
  • VMKernel datamover starts the initial copy of migration from source datastore to destination datastore. Than Mirror driver kicks in that mirror’s I/O between source to destination.
  • As I/O mirroring is in place, vSphere makes a single pass copy of virtual disks from source to destination datastore. And the changes made in between this process are been properly taken care by mirror driver by ensuring all the changes are been reflected on destination datastore also.
  • Once the virtual disk copy gets completed, vSphere quickly suspends and resumes in order transferring control to the shadow VM on the datastore.
  • Once it is confirmed that VM is working properly on the destination datastore, the files on the source datastore gets deleted.


What are the benefits of SVMotion?

  • Using storage VMotion, you can balance utilization on datastores.
  • SVMotion doesn’t require any downtime, so this becomes very helpful during storage upgradation or during any activity on storage side.
  • Using SVMotion you can convert thick disk to thin disk and vice versa.
  • Dynamically optimize storage I/O performance.



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