By Crystal / Last Updated April 24, 2022

How large is VMware snapshot size

Snapshot is similar to a rolling back point used to protect VM when error occurs. When a snapshot is taken, it creates. vmdk, -delta.vmdk, .vmsd, and .vmsn files. The original disk remains read-only, all changes are directed into the new -delta.vmdk files.

Generally, an initial and small snapshot size in VMware is 16 MB, and the size can never grow beyond the original disk file size.

Although the initial snapshot size in VMware is usually small under 100 MB, if it includes memory state, the size of snapshot becomes large in the .vmsn file. The growth of snapshots depends on how many disk changes happen on the virtual machine which should not be underestimated.

vmware snapshot szie

Impacts of snapshot size in VMware

As for VMware snapshots, there is a maximum of 32 snapshots in a VMware chain, but we only recommend 2-3 snapshots instead of 32 and keep them no more than 72 hours. With time passing by, the number and size of snapshot files will grow rapidly, eventually consuming huge amounts of storage space which directly impact the performance of virtual machine.

To conserve disk space, administrators need to continuously manage snapshot growth per VM, and delete those high-capacity snapshot files that may not be of use any longer.

How to calculate snapshot size in VMware

You may know that snapshots are small at first, but it grows rapidly in production environment. So many users may be curious about how to estimate the size of snapshots, but generally speaking, this is no formula and cannot be calculated precisely.

However, here is a tip to calculate disk capacity of VM to estimate how many snapshots you can take in total, because as we said in the former part, the size of VMware snapshots can never grow beyond the original disk file size.

Here is the formula to calculate capacity:

(Size of virtual machine's hard disk(s)) + (size of RAM for virtual machine) + (100 MB for log files per virtual machine).

Estimating the capacity avoids failure in taking snapshots in the case of insufficient space of VM.

How to manage snapshot size in VMware

After calculating VM’s capacity and taking snapshots, you may forget to manage snapshots that exist in your VM or find it difficult to locate the useless snapshots precisely per VM. This process takes much time and energy to locate snapshots and monitor snapshots size in VMware, especially for business.

To avoid time-wasting and running out of disk space, you need to find and delete the snapshots timely especially for those that occupied large space and no longer needed.

The part covers how to manage the size of snapshots simply in VMware with in-built features.

Method 1: Delete snapshots from Snapshot Manager

If the -delta.disk is occupied without any space, navigate to the VM you want to manage and choose to delete snapshots.

delete snapshots from snapshot manager

★Delete Snapshot: Removes the snapshot from the Snapshot Manager and consolidates the snapshot files into the parent snapshot disk and merge with the virtual machine base disk.

★Delete All Snapshots: Consolidates all the changes before the current-state icon (You Are Here) to the VM previous base parent disk and removes all snapshots for that virtual machine.

Method 2: Control maximum of VMware snapshot per VM

By default, a virtual machine with a snapshot tree depth of 31 can support up to 496 snapshots in the worst-case scenario. You could modify the maximum number of snapshots to control the snapshot size increasing in VMware. Please refer to the following steps to modify the VM's .vmx configuration file by using vSphere client.

1. Shut down VM

2. Go to Edit Setting >> VM Option >> Advanced >> Edit Configuration >> Add Configuration Params.

3. Enter the name for the new configuration >> Enter the number of snapshots in the unit in the Value column.

modify configuration parameters

4. Click OK to finish the modification.

5. Open VM and take snapshots to check whether the setting is done.

Here, for example, when I take the second snapshot, it fails. You can notice the error alert: An error occurred while the snapshot Exceeded the maximum number of permitted snapshots.

error

Method 3: Use vCenter Alarm to manage VMware snapshot storage

In virtual environment, snapshots in VMware is a wonderful helper for VM protection, but the increasing size of snapshots is an annoying problem.

Removing snapshots seems to be kind of easy in VMware, but how to know the locations and how to deal with the old and heavy-weight snapshots are much more challenging.

This part introduces how to monitor and manage snapshot size via vCenter.

1. Log in the vSphere web client >> Right click the VM that you want to monitor, and click Alarms >> New Alarm Definition.

2. Enter a name and description >> Select the VM in Monitor drop-down menu, select specific condition or state, for example CPU usage >> Enable this alarm >> Next.

use vcenter to set alarm to manage snapshot size

3. In the Triggers section, click VM Snapshot Size(GB) for trigger type >> Is above >> Set  Warning Condition to the snapshot size in GB(such as 20 GB) that should trigger a warning >> Set the Critical Condition to the snapshot size in GB(such as 30 GB) that should trigger a critical alert >> Next.

trigger for alarm

4. Select the action you want to occur when the alarm is triggered, I set send a notification email to manage snapshot size in VMware >> Enter email >> Set frequency >> Click Finish to complete the alarm configuration.

enter email to receive notification

After setting a new alarm for snapshots, you don’t need to worry about the heavy-weight snapshots running out of your disk space any more. When the size of snapshot is beyond your limitation, it will trigger the alarm and get you noticed.

However, if you are managing multiple virtual machines, snapshots cannot be used as a secure method for data protection. You’d better use backup to prevent VM data loss and save VM storage space.

Better protect VMware VM with less space occupation

Snapshots can protect data security of VM, but it cannot replace backup. As we mentioned, taking snapshots continuously will occupy large space, and it is also way to be damage.

So why not use a more reliable and efficient backup tool such as AOMEI Cyber Backup? It can not only back up multiple virtual machines, but also set retention policies to delete old backups automatically. It allows you to keep the new backups without consuming too much space.

In this part, I will use this backup software to perform a secure and efficient backup task.

Less-storage: It is convenient to set up the retention period for each backup to delete the useless and old files regularly.
Backup multiple VMs automatically: It helps to back up multiple virtual machines at the same time and perform the backup task automatically.
Fast backup and recovery: It reduces the VM downtime and financial loss for fast recovery when unpredictable events happened to your virtual machines.

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How to schedule VM backup with retention policy:

1. Click Backup Task >> Create New Task to create an efficient backup task.

create VM backup

2. Enter a name and select the devices for backup. In the page, you are able to select multiple virtual machines at the same time.

select virtual machine

3. Select backup Target for storage. Local path and network path are all available.

backup target

4. Schedule backup and select retention policy. Specify the time for automatic backup and decide how long you want to keep the backup files.

schedule backup

5. Click Start Backup.

6. Click Restore >> Restore to Original/ New Location to achieve fast and complete recovery.

Using AOMEI Cyber Backup is efficient to make up for the shortcomings caused by snapshots. It saves storage and provides a better way for data protection.

Summary

Snapshots in VMware is a convenient way to achieve fast disaster recovery, but large size of snapshots does impact the performance of VM. So, manage VMware snapshot size is necessary for you.

In older to protect VM security well, backup in VMware is the best option.