What is Quiescing for VMware vSphere VMs?

What is Quiescing?

For some, quiescing is essential when capturing snapshots in a virtual environment, while for others, it's merely an optional feature. Regardless of your stance, understanding what it means to quiesce in vSphere is crucial.

vSphere provides a range of tools and features that facilitate effective virtual machine management. It offers an intuitive virtualization environment that is accessible even to those new to virtualization. VMware regularly updates vSphere, adding new features and enhancing support for broader server and VM management capabilities.

On the vSphere platform, you can take snapshots of your virtual machines. These snapshots capture the state and data of your VMs at a specific moment, recording details like the VM's power status, memory, connections, and other pertinent information.

vSphere enables various snapshotting methods and options, allowing you to tailor your snapshots. It also supports the creation of snapshot chains or extensive snapshot trees. One notable feature is "Quiescing," which enables snapshots to be taken without interruption from ongoing activities.

Interruptions during snapshot creation can pose issues when attempting to revert to a previous state. To avoid this, some users prefer to take snapshots when the VM is idle, particularly when not undergoing heavy I/O operations. For instance, taking a snapshot during a file transfer might result in a corrupted file if you later revert to that snapshot. Essentially, any active processes during the snapshot will not be captured accurately.

To circumvent such issues, many opt for quiesced snapshots over memory snapshots. Quiesced snapshots, which are taken when a VM is forced into a stable state for backup, are generally faster to record than memory snapshots. This makes them preferable for ensuring data integrity during backup processes.

Learn more about VMware Snapshots best practices.

Snapshots in VMware vSphere

How Snapshot works in VMware? To some people, quiescing is a must when taking snapshots, and to others, it’s an optional setting. Whichever one you fall into, it is important to understand what it actually means to quiesce in vSphere.

Apparently, vSphere offers very useful tools and features for effective virtual machine management. It provides an intuitive virtualization environment that even novices can easily navigate and use. VMware releases new versions of vSphere to include newer features and extend support for more server and VM management functions.

You can take snapshots of your virtual machines deployed in VMware’s vSphere platform. These snapshots preserve the state and data of your virtual machine(s) at a specific point in time. Information recorded in a snapshot includes a VM’s power status, memory details, connections to the VM, and other useful information.

vSphere offers different snapshotting techniques and options to allow you to customize your snapshots and also record snapshot chains or create extensive snapshot trees. One of the snapshotting features offered by vSphere is “Quiescing,” a feature that lets you run snapshots without the process being interrupted by ongoing activities.

When a snapshot is interrupted due to ongoing processes on the VM, it becomes a problem when you want to revert to the snapshot. Some users prevent this by taking snapshots when the VM is idle and not running any intense I/O activities. For example, if you take a snapshot when a file is being transferred to another VM when you revert to the snapshot, that file will appear as corrupted. So to say, any running action during a snapshot will not recorded.

To avoid this, most people prefer to run quiesced snapshots rather than memory snapshots. Quiesced snapshots are recorded faster than memory snapshots. Quiesced snapshots are snapshots taken when a VM is forced into a stable state for backup (a snapshot).

The whole essence of snapshots in VMware vSphere is to record specific details of a VM at a given time. Snapshots are like “backups,” but not really backups. vSphere offers two main types of snapshots: Memory Snapshot and Quiesced Snapshot.

Creating a Quiesced Snapshot in vSphere

Quiesced snapshot is not the default snapshot selection in vSphere, so if you’d prefer this snapshot to a memory state snapshot, then you should know how to enable it on your vSphere environment. Firstly, you must have VMware Tools running on your virtual server. Once this is done, here is how vSphere will prepare your VM for a quiesced snapshot:

• Using VMware Tools, the VMware Snapshot Provider function creates a new VSS (Volume Snapshot Service) snapshot in the guest operating system.
• The VSS writers then prepare all active applications for the backup
• Transactions get written from memory to disk.
• The VSS reports to the VMware Tools Service that all prerequisite actions are completed.
• Your system is now ready for a quiesced snapshot.

For vSphere 7.0 Users:

If you use vSphere 7.0, you can create quiesced snapshots from the vCenter interface. Simply follow the steps below:

• Step One: Launch vCenter and select a VM you want to backup
• Step Two: Right-click on the VM, and go to Snapshots 🡺 Take Snapshot.
• Step Three: Look towards the bottom of the popup dialogue box and you will notice that Include virtual machine’s memory is checked by default (that’s the Memory-State Snapshot), uncheck it and select Quiesce guest file system.
• Step Four: Click Create and a quiesce snapshot will be taken. To view the snapshot, go to the Snapshots tab, from there, you can revert, edit, or delete the snapshot.

What More?

Quiescing in vSphere is a snapshotting technique that stabilizes the VM first before recording a shot. It is best used for creating restore points for database VMs. Quiescing is not the default snapshot type on vSphere, so you have to select it manually. If peradventure your snapshot files go missing, you can recover them using the guide provided in this article.