Do you know what are snapshots in VMware? VMware snapshots are convenient as quick failsafe rollback points, but have many limitations. In this article I will introduce you how they work, and how to use them properly.
VMware snapshots preserve the state and data of a VM at a specific point in time. The state includes the VM’s power state, disks, memory, and other devices, such as virtual network interface cards.
You can also take a quiesced snapshot in VMware which captures the state of a virtual machine while ensuring data consistency by temporarily pausing all write operations. This is crucial for applications like databases (e.g., SQL Server, Oracle). Quiesced snapshots can be also useful when archiving data or preparing for migrations.
A VMware snapshot can be used to roll back a virtual machine, so many users tend to achieve VMware backup by snapshot. But strictly speaking, they are 2 different concepts.
Simply put, VMware snapshot cannot replace backup. But you can combine the 2 as a VM protection strategy.
| Feature | VMware Snapshot | VM Backup |
| Independence | Dependent on the parent disk | Independent copy of the virtual machine |
| Storage Method | Stores changes in incremental disk files | Creates a complete copy of the VM |
| Performance | Degrade performance if retained long-term | No impact on the original VM performance |
| Usage | Quick rollbacks and short-term recovery | Disaster recovery and long-term storage |
Taking a VMware snapshot, the following files will be created:
When taking a VMware snapshot, the original virtual disk file will become read-only, and a temporary delta disk which points to it will be created, to store all the changes made to the VM afterward.
As more writes are made to the delta disk, it can grow large enough to fill an entire datastore. After the snapshot is deleted, all changes will be merged into the original .vmdk file, and it will return to read-write mode.
Although convenient, VMware snapshots have limitations in practical use. For example, VMware snapshot size greatly affects the performance of a virtual machine system.
Performance degradation depends on how long you keep the snapshots, how deep the snapshots tree is, and how many changes you have made to the VM since you took the snapshot.
For better working with VMware snapshots, here I summarized 3 best practices.
VM snapshot vs backup is a long-confusing issue for VM users. The accepted conclusion is that snapshots cannot be used as backups.
As above stated, while VM backup is an independent copy of the VM, and can be safely stored offsite to the cloud or other locations, snapshots depend on the parent disk. If the base disks are deleted, the snapshot files are not sufficient to restore a VM.
When you create a snapshot for the first time, the first child disk is created from the parent disk. Successive snapshots generate new child disks from the last child disk on the chain.
A maximum of 32 snapshots are supported in a chain. However, for a better performance please use only 2 to 3 snapshots.
Generally, you need to reserve 20-30% extra storage for a single snapshot. As more changes you made to the VM after a snapshot, the delta disk file can even run out of space, and affect the performance of your VM system.
Therefore, please delete the snapshots in time to merge the changes to the parent disk when they are no longer useful, or before creating backups of your VM.
Now you have known when should you take VMware snapshots, and how to keep them in optimal use. The next thing you need to know is the specific steps of the basic VMware snapshots operations.
In this section, I will demonstrate how to perform the basic operations of VMware ESXi snapshots as an example.
1. Access to vSphere Web Client. Right-click on the VM name in the inventory and select Snapshots > Take Snapshot…
2. In the pop-up window, provide a Name and optionally a Description for the snapshot. You can Edit them later in Snapshot Manager.
3. There are 2 options to check:
4. Click OK to take the snapshot. You can see the progress in Recent Tasks.
1. Access to vSphere Web Client. In this step, operations are different according to different needs.
β¦ If you want to revert to the latest snapshot: Right-click on the VM name and select Revert to Latest Snapshot.
β¦ If you want to revert to another previous snapshot: Right-click on the VM name and select Manage Snapshots…
Select the snapshot you want to revert in Snapshot Manager, and click Revert to.
2. It will pop up a Confirm window notifying the loss of the current state. If it is a memory snapshot, then there will be one more option to suspend this VM when reverting to selected snapshot. You need to manually power on the VM later if you check this option.
3. Click Yes to revert to the selected VMware snapshot. In Snapshots Manager you can see the current state represented by You are here.
1. Access to vSphere Web Client. Right-click on the VM name and select Manage Snapshots…
2. In this step, operations are different according to different needs.
β¦ If you want to delete one snapshot: Select the target snapshot and click Delete. Click Yes in the pop-up Confirm window.
β¦ If you want to delete all snapshots: Click Delete All in Snapshot Manager and click Yes in the pop-up Confirm window.
3. Click Close to exit the Snapshot Manager.
While snapshots are useful for short-term changes or quick rollbacks, they are not suitable as a standalone backup solution due to their limitations in independence, performance, and disaster recovery scenarios.
There are different VMware backup solutions to create independent and complete VMware VM backups.
Today, specialized backup tools have emerged to enhance VM backup capabilities, addressing limitations of VMware's built-in features.
For example, AOMEI Cyber Backup is a free VMware backup software, offering robust and user-friendly VMware backup options. This free software enables automatic backups of multiple VMs across both paid and free versions of VMware ESXi, making it a popular choice among VM users.
| π©Centralized Management: A centralized web console to manage your VMware virtual machines regardless of sockets and hosts. | πFast Disaster Recovery: Restore the entire VMware VM to a usable state quickly without re-creating and configurating a new VM, greatly reduce business downtime and possible financial loss. |
| π±π»Role-Based Management: Assign other team members with different permissions to team-up efficiently and safely. |
π Automatic Backup Cleanup: Keep backups up to date and remove old backup versions automatically to save storage space. |
Click the button below to download the the freeware of AOMEI Cyber Backup and get started!
*You can choose to install this VM backup software on either Windows or Linux system.
Step1. Bind Devices
Access to AOMEI Cyber Backup web client, navigate to Source Device > VMware > + Add VMware Device to add vCenter or Standalone ESXi host as the source device, and then click … > Bind Device.
Note: This step is only needed when you bind the host for the first time, you do not need to repeat after successful binding.
Step 2. Create Backup Tasks
βNavigate to Backup Task > + Create New Task, and provide Task Name, Backup Type, Device, Target, and Schedule as needed.
Step 3. Start Backup
Click Start Backup to select to Add the schedule and start backup now, or Add the schedule only.
Created backup tasks will be listed separated for further log checking, task changing, or restoring.
While the Free Edition covers most of VM backup needs, you can also upgrade to enjoy: βΆ Batch VM Backup: batch backup large numbers of VMs managed by vCenter Server or standalone ESXi hosts. βΆ Backup cleanup: Configure a retention policy to auto delete old backup files and save storage space. βΆ Restore to new location: Create a new VM in the same or another datastore/host directly from the backup, saves the trouble of re-configuring the new VM.
Many people confuse VMware backup with snapshots. In fact, they are 2 different things. Although VMware snapshots are convenient for quickly rolling back the VM to a specific point in time, they cannot replace backups, and need to be used properly to maintain the VM system performance.
In this article, I introduced what are snapshots and the best practices to use them, including the detailed steps of how to create, revert, and delete them. Snapshots cannot replace backups, but using them in conjunction with backups can greatly improve your work efficiency.
To properly backup VMware ESXi VMs, you can choose AOMEI Cyber Backup to help you schedule automatic backup tasks for multiple VMs. Except for VMware ESXi VMs, it also supports Microsoft Hyper-V.