Troubleshoot storage errors

This article helps you identify and resolve common storage errors in the Video Management System (VMS). The VMS lists these errors as Storage Failure events in the Event Log.

Note: The VMS reports these errors, but the cause is usually the storage hardware or how the server is configured, not the VMS itself. Nx Support can't troubleshoot or repair storage hardware.

System disk is almost full

This error appears when the free space on the operating system partition falls below:

• 5 GB on x64 devices
• 1 GB on ARM devices

Why it happens

The operating system and the Media Server both need free space on the system partition to work correctly. The Media Server stores critical data on the system partition, including:

• The Site database
• Motion detection indexes
• Audit logs

In most cases, the space is taken by data that doesn't belong to the VMS, or the system drive is too small for the server's workload.

How to fix it

1. Remove applications and files that the server doesn't need.
2. Clear cached data that grows over time, such as Desktop Client cache folders and operating system logs.
3. Make sure that video archives record to a secondary drive, not the system partition.
4. If the system drive is still too small, replace it with a larger drive.

Not enough HDD/SSD speed for recording

This error appears when a storage drive can't write data as fast as the incoming video arrives. Depending on your version, the notification reads Not enough HDD/SSD speed for recording to [drive_name] or Not enough HDD/SSD/Network speed for recording.

Why it happens

The Media Server holds incoming video frames from each camera stream in a memory buffer before it writes them to disk. If the drive falls behind, the buffer fills up and the Media Server drops the oldest frames. Dropped frames are never written, so this error means that footage is lost.

The drives themselves are rarely at fault. Common causes include:

• Other software reading from or writing to the archive drive, such as antivirus scans, file indexing, shadow copies, backups, or disk defragmentation
• Analytics data stored on the same drive as the video archive
  It is recommended to assign the analytics database to a dedicated SSD or NVMe drive. 
• Recording to the system drive
• Reserved space that's too small for the drive. You should keep a buffer of approximately 10%. 
• An archive reindex running in the background
• A slow or unstable connection to network storage
• A failing drive or a degraded RAID array
• More cameras or a higher bitrate than the storage can handle

Decide how urgent it is

How you respond depends on how often the error appears:

• Occasional errors with few dropped frames: The server is working close to its storage limit. Before you add cameras or increase stream quality, increase your storage capacity.
• Persistent errors or many dropped frames: The server is losing footage. Work through the possible fixes in the next section.

How to fix it

Work through these fixes in order. The first fixes resolve most cases and are the least disruptive.

Exclude the archive from antivirus scanning

Real-time antivirus protection scans every video file that the Media Server writes, which competes with recording. Microsoft Defender is turned on by default on Windows, even when no other antivirus is installed.

1. Add the Nx Witness folders and every archive folder to your antivirus exclusion list. For the full list, see Configuring antivirus exclusions for Nx Witness.

2. If you use Microsoft Defender, open PowerShell as an administrator and run the following commands. Replace the placeholders with your archive paths:

   Add-MpPreference -ExclusionPath "D:\<archive folder>"
   Add-MpPreference -ExclusionPath "\\<nas>\<share>"
   Add-MpPreference -ExclusionProcess "mediaserver.exe"
   Add-MpPreference -ExclusionExtension "mkv"
   Add-MpPreference -ExclusionExtension "nxdb"

3. To confirm the exclusions, run:

   Get-MpPreference | Select-Object Exclusion*

Stop other Windows tasks on the archive drives

1. Turn off indexing: In File Explorer, right-click the archive drive and select Properties. Clear Allow files on this drive to have contents indexed in addition to file properties, and then apply the change to all subfolders and files.

2. Turn off shadow copies for the archive drive. To see which drives have shadow copies, run the following commands in PowerShell:

   vssadmin list shadowstorage
   vssadmin list shadows

3. Turn off scheduled defragmentation for the archive drives in Optimize Drives.
4. Check Task Scheduler and your backup software for jobs that read from the archive drives. If the error appears at the same time every day or every week, a scheduled job is the likely cause.

Move analytics and motion data to a separate drive

Analytics and motion data can write heavily to the same drive as your video. Store this data on a separate drive, preferably an SSD.

1. In the Desktop Client, open Server Settings and go to the Storage Management tab. 
2. Select the dedicated SSD or NVMe drive that doesn't store the video archive.
3. Click Apply.

Check the storage configuration

• Don't record to the system drive. Recording to the operating system drive competes with Windows, the page file, updates, and antivirus scans.
• Set the reserved space to at least 10% of each drive. Sites installed before version 5.1.5 used a smaller default, and the new default applies only to storage added after the update. For steps, see Adjust the reserved disk space. After you change it, the Media Server needs time to delete old footage, which can take one to two days.
• Use one server per archive folder. Make sure that no other server records to the same folder or network share.

Let an archive reindex finish

An archive reindex reads the whole archive and can cause this error on its own. A reindex starts after you add, re-add, or reconnect storage. If a reindex is running, let it finish. A large archive can take many hours.

Check drives, RAID arrays, and network storage

1. Check the health and SMART status of each archive drive, and replace failing drives.
2. If you use RAID, check the RAID controller for failed or degraded drives.
3. If you use network storage, make sure that it stays online and connects over a stable link of at least 1 Gbps. A slower link can't keep up when the Media Server records and backs up to the same storage.
4. If your network storage supports it, use iSCSI instead of SMB shares, and turn off the recycle bin on the network share.

Reduce the load or add storage

If the error continues after the previous fixes, the storage can't handle the amount of video. Do one or more of the following:

• Lower the bitrate by reducing the resolution or frame rate in camera settings.
• Add drives to spread the write load.
• Replace existing drives with faster models.
• Move some cameras to another server.

I/O error occurred

This error means that the operating system couldn't read from or write to a drive because of a physical or logical failure.

Why it happens

Common causes include:

• Bad sectors or a hardware failure on a local drive
• A drive that remounts as read-only because of file system corruption
• Network storage that disconnects or becomes unreachable
• A drive or network share that runs out of free space
• Several servers that record to the same network share

How to fix it

1. Check the drive status and SMART data for hardware failures.
2. Reconnect or test the cables, ports, and network connections for external storage.
3. If a drive or network share is full, free up space on it, and make sure that only one server records to it.
4. Replace failing drives, or repair corrupted file systems with your operating system's disk tools.