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Not Enough Space on Volume for Snapshot Storage

Not Enough Space on Volume for Snapshot Storage

Category: Acronis Troubleshooting | Disk Space & VSS Issues
Priority:HIGH
Last Updated:November 2025

Problem

Acronis backup operations fail because the Volume Shadow Copy Service (VSS) cannot allocate sufficient space to store temporary snapshots during the backup process. VSS creates point-in-time snapshots of volumes being backed up, and these snapshots require storage space to track changes that occur during the backup operation.

When available disk space is insufficient, VSS cannot create or maintain the snapshot, causing the entire backup to fail. This issue is particularly common on systems with high I/O activity, limited free disk space, or when backing up volumes that undergo significant changes during backup operations.

Symptoms

Error Messages During Backup

You may encounter one or more of these error messages when attempting disk, partition, or file-level backups:

Standard Error Messages: - Not enough space to create a volume snapshot on the volume where the snapshot storage is located. - Not enough space to create a volume snapshot on the volume where the snapshot storage is set. - There is not enough space on the volume where the snapshot storage is located. - Failed to create VSS snapshot for volume [Drive Letter]

Windows Event Log Errors

Check Event Viewer → Windows Logs → System for related VSS errors:

Event ID 25 (VolSnap):

Source: VolSnap Event ID: 25 Level: Error Message: The shadow copies of volume G: were deleted because the shadow copy storage could not grow in time. Consider reducing the IO load on the system or choose a shadow copy storage volume that is not being shadow copied.

Event ID 8193 (VSS):

Source: VSS Event ID: 8193 Level: Error Message: Volume Shadow Copy Service error: The shadow copy storage area is full. To make room, delete older shadow copies or increase the size of the shadow copy storage area.

Backup Behavior

  • Backup starts normally and appears to be progressing

  • Failure occurs during snapshot creation phase (usually within first few minutes)

  • Error appears consistently on the same volume(s)

  • Incremental backups may fail more frequently than full backups

  • Issue worsens during periods of high system activity

System Impact

  • Disk space warning indicators may appear in Windows

  • System performance may degrade during backup attempts

  • Multiple backup retries consume additional disk space

  • Shadow copies accumulate and further reduce available space

Solution

Quick Assessment

Before proceeding with solutions, assess the current situation:

Check Available Disk Space:

wmic logicaldisk get caption,freespace,size

Check Current Shadow Storage Configuration:

vssadmin list shadowstorage

View Existing Shadow Copies:

vssadmin list shadows

Solution 1: Free Up Disk Space (Recommended First Step)

Increase available space on the source volume before attempting other solutions.

1a. Run Disk Cleanup: 1. Press Win + R, type cleanmgr, press Enter 2. Select the drive that's running out of space 3. Check all available options, including: - Temporary files - Windows Update cleanup - Recycle Bin - System error memory dump files 4. Click OK to clean

1b. Remove Unnecessary Files: - Delete old log files - Move large media files to different volumes - Uninstall unused applications - Clear browser caches and downloads

1c. Clean Temp Directories:

del /q /f /s %TEMP%\* del /q /f /s C:\Windows\Temp\*

1d. Remove Old Shadow Copies:

vssadmin delete shadows /For=C: /Oldest

Or delete all shadow copies (use with caution):

vssadmin delete shadows /For=C: /All

Solution 2: Increase Shadow Storage Allocation

Adjust the maximum size allocated for shadow copies.

2a. Check Current Allocation:

vssadmin list shadowstorage

Example Output:

For volume: (C:)\?\Volume{guid} Shadow Copy Storage volume: (C:)\?\Volume{guid} Used Shadow Copy Storage space: 1.815 GB (1%) Allocated Shadow Copy Storage space: 2.315 GB (1%) Maximum Shadow Copy Storage space: 2.419 GB (1%)

2b. Increase Maximum Size:

vssadmin resize shadowstorage /For=C: /On=C: /MaxSize=20GB

Recommended Sizes: - Workstations: 10-20GB - Servers with moderate I/O: 20-50GB - Servers with high I/O: 50-100GB - Database servers: 100GB or UNBOUNDED (use with caution)

Set Unbounded (No Limit):

vssadmin resize shadowstorage /For=C: /On=C: /MaxSize=UNBOUNDED

⚠️ Warning: UNBOUNDED can consume all available disk space. Monitor carefully.

Solution 3: Move Shadow Storage (Server OS Only)

⚠️ IMPORTANT: This functionality is ONLY available on Windows Server editions (2008 R2, 2012, 2016, 2019, 2022). It is NOT available on Windows desktop editions (7, 8, 8.1, 10, 11).

Move shadow storage to a different volume with more available space.

3a. Verify Current Configuration:

vssadmin list shadowstorage

3b. Delete Existing Shadow Storage Association:

vssadmin delete shadowstorage /For=C: /On=C: /Quiet

3c. Create New Shadow Storage on Different Volume:

vssadmin add shadowstorage /For=C: /On=D: /MaxSize=50GB

Parameters: - /For=C: - The volume being backed up (source volume) - /On=D: - The volume where shadow storage will be placed (target volume) - /MaxSize=50GB - Maximum space allocated for shadows

3d. Verify New Configuration:

vssadmin list shadowstorage

Best Practices for Separate Volume: - Use a volume with ample free space (100GB+ recommended) - Prefer fast storage (SSD over HDD if available) - Ensure the target volume is not being backed up simultaneously - Monitor target volume space regularly

Solution 4: Schedule Backups During Low Activity

Reduce I/O contention by timing backups strategically.

4a. Identify Low-Activity Periods: - Review system performance history - Use Performance Monitor to track disk I/O patterns - Identify nights, weekends, or off-peak hours

4b. Reschedule Backups: 1. Open Acronis management console 2. Navigate to Protection Plans 3. Select the failing backup plan 4. Click Schedule or When to backup 5. Adjust schedule to low-activity periods: - Weeknights after business hours (e.g., 11 PM - 5 AM) - Weekends - Maintenance windows

4c. Stagger Multiple Backups: If backing up multiple volumes or systems: - Don't schedule all backups simultaneously - Space backups 30-60 minutes apart - Prioritize critical systems during optimal windows

Solution 5: Optimize Backup Configuration

Adjust Acronis settings to reduce snapshot storage requirements.

5a. Use File-Level Backup Instead: For data-only volumes, consider file-level backup: 1. Create new backup plan 2. Select Files and Folders instead of Disk/Partition 3. Choose specific files/folders to backup 4. File-level backups create smaller snapshots

5b. Exclude Unnecessary Data: 1. Edit backup plan 2. Go to Backup options → Exclusions 3. Exclude: - Page file (pagefile.sys) - Hibernation file (hiberfil.sys) - Temporary directories - Cache folders - Non-critical data

5c. Adjust Backup Compression: Higher compression reduces data size but increases processing time: 1. Backup options → Compression level 2. Select High or Maximum 3. Test to ensure completion within acceptable timeframe

Solution 6: Temporarily Stop High I/O Applications

Reduce I/O load during backup operations.

Before Backup: - Close database applications - Stop file indexing services - Pause antivirus scans - Stop Windows Search service: net stop wsearch - Stop Windows Update service: net stop wuauserv

Create Pre/Post Backup Scripts:

Acronis allows command execution before/after backups:

Pre-backup script (stop_services.cmd):

@echo off net stop wsearch net stop wuauserv net stop BITS

Post-backup script (start_services.cmd):

@echo off net start wsearch net start wuauserv net start BITS

Attach these scripts in Acronis backup plan options.

Prevention

Proactive Disk Space Management

1. Maintain Adequate Free Space

Establish and enforce minimum free space policies: - System volumes: Maintain 15-20% free space minimum - Data volumes: Maintain 10-15% free space minimum - Servers: Maintain 20-30% free space minimum

2. Implement Automated Monitoring

PowerShell Monitoring Script:

# Check disk space and alert if below threshold $threshold = 15 # percentage Get-WmiObject Win32_LogicalDisk -Filter "DriveType=3" | ForEach-Object { $percentFree = ($_.FreeSpace / $_.Size) * 100 if ($percentFree -lt $threshold) { Write-EventLog -LogName Application -Source "Disk Monitor" ` -EventId 1001 -EntryType Warning ` -Message "Drive $($_.DeviceID) has only $([math]::Round($percentFree,2))% free space" # Send email alert here } }

Schedule this script to run daily.

3. Configure Storage Sense (Windows 10/11)

Automate cleanup on desktop systems: 1. Settings → System → Storage 2. Enable Storage Sense 3. Configure to run: - Every week - Delete temporary files older than 14 days - Empty Recycle Bin after 30 days

VSS Configuration Best Practices

1. Right-Size Shadow Storage

Don't use default sizes—configure based on usage:

# For typical workstation vssadmin resize shadowstorage /For=C: /On=C: /MaxSize=10GB # For busy server vssadmin resize shadowstorage /For=C: /On=C: /MaxSize=50GB

2. Regular Shadow Copy Cleanup

Create scheduled task to clean old shadows:

Weekly cleanup script (cleanup_shadows.cmd):

@echo off echo Cleaning old shadow copies... vssadmin delete shadows /For=C: /Oldest /Quiet vssadmin delete shadows /For=D: /Oldest /Quiet echo Cleanup complete vssadmin list shadows

3. Monitor Shadow Storage Usage

Create monitoring dashboard:

vssadmin list shadowstorage > C:\Reports\VSS_Status_%date:~-4,4%%date:~-10,2%%date:~-7,2%.txt

Review reports weekly for trends.

Backup Schedule Optimization

1. Identify Optimal Backup Windows

Use Performance Monitor to track: - Disk I/O rates over 24-hour periods - CPU usage patterns - Network utilization

Schedule backups when these metrics are lowest.

2. Implement Backup Rotation

Don't backup everything every day: - Critical systems: Daily backups - Important systems: Every 2-3 days - Archival systems: Weekly backups - Rotate schedules to distribute load

3. Use Differential/Incremental Backups

After initial full backup: - Use incremental backups (only changed data) - Reduces backup time and I/O load - Requires less snapshot storage

Configure in Acronis: 1. Backup plan → Schedule 2. Select backup scheme: Incremental or Differential 3. Set retention policy appropriately

System Capacity Planning

1. Regular Capacity Review

Monthly review schedule: - Analyze disk space trends - Project future space needs - Plan for storage expansion

2. Allocate Shadow Storage Proactively

When adding new volumes:

# Immediately configure shadow storage vssadmin add shadowstorage /For=E: /On=E: /MaxSize=20GB

3. Separate System and Data

Architecture best practice: - C: - Operating system and applications - D: - User data and files - E: - (Optional) Shadow storage destination - Backup schedules can be optimized per volume

Hardware Considerations

1. Storage Upgrades

If issues persist despite optimization: - Add additional physical drives - Upgrade to larger capacity drives - Implement SAN/NAS storage - Use faster storage (SSD) for shadow copies

2. I/O Optimization

  • Use RAID configurations appropriate for workload

  • Ensure disk controllers have adequate cache

  • Update storage drivers regularly

  • Enable write caching if safe to do so

3. Dedicated Shadow Storage (Servers)

On servers, consider: - Dedicated volume for shadow storage - Separate physical disks from source volume - Use faster storage tier for shadows

Understanding VSS and Snapshots

What is Volume Shadow Copy Service (VSS)?

VSS is a Windows service that: - Creates point-in-time snapshots of volumes - Enables consistent backups of open/locked files - Coordinates with applications for transactional consistency - Manages temporary storage for changed data during backup

How Snapshots Work

  1. Snapshot Creation: VSS creates a read-only point-in-time view of the volume

  2. Copy-on-Write: Original data blocks are copied to snapshot storage before being modified

  3. Space Consumption: More changes during backup = more snapshot storage needed

  4. Snapshot Release: After backup completes, snapshot is deleted and space reclaimed

Why Snapshots Fail with Low Space

  • Snapshots use copy-on-write mechanism

  • Every write operation during backup requires snapshot storage

  • High I/O activity = rapid snapshot storage consumption

  • If storage exhausted, snapshot becomes invalid

  • Invalid snapshot = backup failure

Windows Desktop vs. Server Limitations

Windows Desktop (7, 8, 10, 11): - ❌ Cannot move shadow storage to different volume - ❌ Shadow storage location fixed to source volume - ✅ Can resize shadow storage allocation - ✅ Can increase maximum size

Windows Server (2008 R2 and later): - ✅ Can move shadow storage to different volume - ✅ Full shadow storage management - ✅ Can resize and relocate - ✅ Advanced VSS configuration options

Troubleshooting Decision Tree

Backup failing with space error? │ ├─ Check available free space on source volume │ ├─ < 10% free → Free up space (Solution 1) │ └─ > 10% free → Continue │ ├─ Check shadow storage allocation │ └─ vssadmin list shadowstorage │ ├─ MaxSize too small → Resize (Solution 2) │ └─ MaxSize adequate → Continue │ ├─ Server OS? │ ├─ YES → Can move to different volume (Solution 3) │ └─ NO → Desktop OS, cannot move │ ├─ High I/O during backup? │ ├─ YES → Reschedule to low-activity period (Solution 4) │ └─ NO → Continue │ └─ Optimize backup configuration (Solution 5) └─ Consider file-level instead of disk-level

Additional Resources

  • Backup fails with VSS errors

  • Event ID 25 VolSnap errors

  • Shadow copy creation failures

  • Disk space exhaustion during backup

  • Volume Shadow Copy Service errors

  • Incremental backup failures

Keywords

not enough space, snapshot storage, VSS error, shadow copy, volume snapshot, disk space, backup fails, vssadmin, Event ID 25, VolSnap, shadow copy storage full, snapshot storage full, VSS snapshot failed

Need Additional Help?

If these solutions don't resolve the issue: 1. Check Event Viewer for additional VSS errors 2. Review disk performance with Performance Monitor 3. Verify disk health with chkdsk /f 4. Check for disk fragmentation 5. Collect Acronis logs from C:\ProgramData\Acronis\Agent\var\log\ 6. Review VSS logs in Event Viewer under Applications and Services → Microsoft → Windows → VSS 7. Contact Acronis Support with collected diagnostics