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By: Emma

What Is a Snapshot in VMware and How It Works

A VMware snapshot is a point-in-time capture of a virtual machine’s state, giving you a restore point to fall back on if something goes wrong.

When you take a snapshot, VMware freezes the original virtual disk and makes it read-only. All new writes are redirected to a delta disk (the -delta.vmdk file), which grows continuously as the VM generates data. VMware also creates a .vmsn file to store the VM’s state metadata, which is what allows you to revert to that exact point in time.

what is vmware snapshot

Three States Captured

A VMware snapshot can capture up to three layers of a VM’s state:

  • Disk state: a point-in-time image of the virtual hard drive
  • Memory state: active RAM and running processes, so you can revert to a live, powered-on state
  • Power state: whether the VM was on, off, or suspended at the time of the snapshot

Snapshots vs. Backups

  • A snapshot depends entirely on the original base disk, if that disk is lost or the datastore fails, the snapshot is gone too.
  • A backup is an independent copy stored on a separate infrastructure for data recovery. If data is lost or corrupted in your VMware environment, the amount of data that can be recovered depends on the amount of data you have backed up.

Think of snapshots as short-term undo buttons: useful before a patch or config change, but not a substitute for disaster recovery. 

Tip: To know more about the differences between snapshots and backups, you can refer to: Backup vs Snapshot: What’s the Difference?

How to Schedule Snapshots in VMware with 2 Methods

You can automate VMware snapshot scheduling using either the built-in vSphere interface or PowerCLI scripting. The right choice depends on your environment’s scale and how much flexibility you need.

Method 1: vCenter Scheduled Tasks

The vCenter scheduler is the most straightforward option for administrators who prefer a graphical interface. It works well for single-VM schedules and simple recurring tasks.

Prerequisites

  • vCenter Server required: standalone ESXi hosts do not support the full scheduled task feature set
  • Permissions: your account needs Scheduled Task: Create/Modify/Delete and Virtual Machine: Snapshot Management privileges
  • Timezone: the scheduler runs on vCenter Server’s timezone; if your workstation is in a different region, account for the offset when setting the time

Step-by-step (vSphere 6.5 / 6.7 / 7.x / 8.x)

  1. Log in to the vSphere Web Client and navigate to the target VM.
  2. Click the Monitor tab, then go to Tasks & EventsScheduled Tasks.
  3. Click Schedule a New Task and select Take Snapshot from the dropdown.
  4. Enter a descriptive name (e.g., “Weekly-Maintenance-Snapshot”) and an optional description.
  5. Set your desired frequency: Once, Daily, Weekly, or Monthly.
  6. Configure the timing and click Finish.

take snapshot -vmware snapshot

Tip: Select the task and click Run Now to verify it works before relying on the schedule.

How to Edit or Delete an Existing Scheduled Task

Scheduled tasks can be modified or removed without affecting the underlying VM. In the Scheduled Tasks pane, you can view the history of each task — including start time, end time, and status, and make changes at any time. Snapshots already created by the task are not affected.

GUI Limitations

The vCenter scheduler is convenient for basic use, but it has real limitations. It cannot handle conditional logic, has no built-in auto-deletion for aging snapshots, and offers no native alerts if a scheduled task fails.

Method 2: PowerCLI Scheduled Snapshots

When managing dozens or hundreds of VMs, the vCenter GUI becomes inefficient. PowerCLI lets you automate snapshot creation across your entire inventory, with support for conditional logic and automated cleanup.

When to use PowerCLI

PowerCLI is the better choice for multi-VM environments where you need consistent naming conventions or bulk operations. It’s also the only native option for automating snapshot deletion — something the vCenter GUI cannot do on its own.

Prerequisites

Install the VMware PowerCLI module and connect to your vCenter Server before running any scripts:

Install-Module -Name VMware.PowerCLI

Connect-VIServer -Server "vcenter_server_name"

powercli scheduled snapshots prerequisities

Create a Snapshot for a Single VM

The following command creates a snapshot with a date-stamped name. The -Quiesce flag requests a file system freeze from VMware Tools, producing an application-consistent snapshot. The -Memory flag captures the live RAM state.

New-Snapshot -VM "VM_Name" -Name "Pre-Patch-$(Get-Date -Format yyyyMMdd)" -Quiesce -Memory -RunAsync

create a snapshot for a single vm

Note:-Quiesce requires VMware Tools to be installed and running on the guest OS. If Tools are absent or the OS doesn’t support quiescing, the flag will be ignored or the command may fail.

-RunAsync sends the task to the background so the PowerShell prompt remains available immediately.

Bulk-Snapshot All Running VMs

To snapshot all powered-on VMs at once, filter by power state before piping into the snapshot cmdlet:

Get-VM | Where-Object {$_.PowerState -eq "PoweredOn"} | New-Snapshot -Name "DailySafety" -RunAsync

bulk-snapshot all running vms

Auto-Delete Old Snapshots

Forgotten snapshots grow continuously and can exhaust datastore space — a problem known as snapshot sprawl. Use the following script to remove snapshots older than a defined threshold:

# Delete snapshots older than 3 days

Get-VM | Get-Snapshot | Where-Object {$_.Created -lt (Get-Date).AddDays(-3)} | Remove-Snapshot -Confirm:$false

auto-delete old snapshots

Schedule this script via Windows Task Scheduler to run daily, and snapshot sprawl becomes a non-issue.

Go Beyond Snapshots: Scheduled Backups with i2Backup

Snapshots are useful for short-term rollbacks, but they are not a substitute for a real backup strategy. If a datastore fails or a snapshot chain becomes corrupt, there is nothing to fall back on.

For production environments, scheduled backups to independent storage are essential — and that is where dedicated backup software like i2Backup comes in.

Key Features of i2Backup

  • Flexible Scheduling: i2Backup lets you configure backup schedules that match your business rhythm on a virtual console— hourly, daily, weekly, monthly, or yearly. Once the rules are in place, everything runs automatically in the background. 
  • Agentless VM Backup: i2Backup protects VMware virtual machines without requiring agents to be installed on each guest. It uses native virtualization platform APIs to perform backup, replication, and migration with no impact on running workloads. It is also fully compatible with Hyper-V, OpenStack, and other mainstream virtualization platforms.
  • Automated Retention Management: i2Backup applies customizable retention policies to remove outdated backups automatically. This keeps storage usage under control without requiring manual cleanup.
  • Point-in-Time Recovery: i2Backup captures continuous backup logs and supports multiple restore points. Whether the issue is accidental deletion or data corruption, you can recover to a precise moment in time.
  • Instant VM Recovery: In the event of a server failure, i2Backup can remotely mount a VM backup to the target platform immediately, achieving ultra-low recovery time objectives without waiting for a full restore.

Snapshots capture a moment. Backups protect your data and business. For environments where data loss is not an option, pairing your VMware snapshot schedule with i2Backup’s automated backup jobs gives you both short-term rollback capability and long-term disaster recovery coverage.

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Best Practices for Scheduling VMware Snapshots

Automating snapshots removes the manual effort, but it also makes it easier for problems to quietly accumulate. These practices help you stay ahead of storage issues and keep your snapshot strategy reliable.

Keep snapshots short-lived

Snapshot delta files grow continuously as the VM writes new data. VMware recommends keeping snapshots under 72 hours — beyond that, delta files can grow large enough to exhaust the datastore and impact VM performance.

Limit the snapshot chain

VMware officially supports up to 32 snapshots in a chain, but performance degrades well before that limit. Keep the active chain to 2–3 snapshots at most.

Be cautious with I/O-heavy VMs

Database VMs and other write-intensive workloads generate data changes rapidly. Snapshots on these VMs can fill a datastore much faster than expected, causing application latency and potential failures.

Snapshots are not backups

Snapshots are temporary delta files tied to the base disk. If the base disk is lost or the datastore fails, snapshots go with it. Use dedicated backup software like Info2soft‘s i2Backup for long-term disaster recovery coverage.

Configure vCenter Alarms

Set up alarms to alert you when a snapshot exceeds a defined age or size threshold. Alarms can also trigger automatic cleanup actions, giving you an additional safety net on top of your scheduled scripts.

Troubleshooting Common Scheduled Snapshot Issues

Even with automation in place, things can go wrong. Here are the most common issues administrators run into when scheduling VMware snapshots — and how to fix them.

Issue 1: Scheduled task exists but the snapshot never fires

The most likely cause is a timezone mismatch between the vCenter Server and your local time.

Check the vCenter system clock to confirm the task isn’t scheduled hours off target. Also verify that the service account running the task still has Virtual Machine: Snapshot Management permissions — these can be lost after account changes or role updates.

 

Issue 2: VM performance drops after scheduled snapshots

As a snapshot ages, its delta file grows. The larger it gets, the more I/O the host needs to perform to reconcile reads between the base disk and the delta.

If you notice latency after a scheduled snapshot, check for large or aging delta files and run a Consolidate operation immediately to merge them back into the base disk.

 

Issue 3: Corrupt snapshot chain that can’t be deleted via the GUI

If the vSphere Client fails to delete a snapshot — often accompanied by “CID mismatch” errors — try forcing consolidation using vmkfstools from the ESXi command line or via PowerCLI. If the chain is too damaged to repair, restore the VM from a recent backup.

 

Issue 4: Snapshot fails on a powered-on VM with independent disks

VMware does not support snapshots of disks configured as Independent-Persistent or Independent-Nonpersistent while the VM is running.

If your scheduled task fails with a disk-related error, either power off the VM before the snapshot runs or change the disk mode to Dependent in the VM settings.

 

Issue 5: Datastore space alert triggered by growing snapshots

If snapshots are being created faster than they are deleted, storage will eventually run out — and when a datastore fills up, all VMs on that volume will pause. If an alert fires, run your PowerCLI cleanup script immediately and tighten your retention policy so old snapshots are purged more aggressively.

Conclusion

Scheduling VMware snapshots — whether through vCenter Scheduled Tasks or PowerCLI — reduces manual overhead and helps protect your VMs before patches, updates, or configuration changes. But automation alone is not enough.

Pair your snapshot schedule with automated deletion scripts and vCenter alarms to prevent storage exhaustion. And for long-term data protection, treat snapshots as a short-term tool and rely on dedicated backup software like i2Backup for disaster recovery coverage. That combination gives you both agility and resilience.

Emma
Emma is the bridge between complex engineering and the people who need it. As a content creator at Info2Soft, she spends her days translating "tech-speak" into clear, actionable stories about data resilience. She’s not just documenting software; she's uncovering how data replication and recovery actually change the way businesses run.
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