This short guide covers the most common storage-related errors Users might be met with while using Nx Witness. Such errors are referred to as "Storage Failure" in the event log.

"System disk is almost full".

This error appears if the Nx Mediaserver detects that the free space of the Server partition drops under 1 GB for ARM devices and under 5 GB for x64 devices.

Network Optix considers it as an issue that should be resolved because both the OS and the Nx System might suffer significantly due to that. Although it is understandable why the OS needs a lot of free space, Nx Witness needs it because it keeps important data in the system partition (e.g. system database, motion detection data indexes, audit log, etc.).

"Not enough HDD/SSD speed for recording to %drive_name%".

During the regular recording process, the Nx Mediaserver keeps all video frames received from every camera stream in separate buffers. Later, the other part of Nx Server tries to write the frames from such buffers to the physical drive. These buffers have certain reasonable limits, independently in megabytes and number of frames.

If for whatever reason the storage drive write speed can not match the rate of incoming video packets/frames, these buffers might overflow. When this happens, Nx Server has to drop the oldest packages. After that, the error is generated with the number of the dropped frames. Users might find which camera feed specifically suffered from this by reading the main Nx Server log file.

If a user receives such messages randomly, from time to time with a low number of packets dropped, there's nothing to worry about right now. Essentially, it signals that the System is near its limits. So if a user is planning to expand the System, he should expect that number of dropped packages will drastically increase and resolve it in advance. The available options are to decrease incoming bitrate by playing with fps/image quality, replace drives with faster ones, or simply add more drives.

If a user receives such messages all the time, it is something to worry about, since a significant part of the footage is likely persistently lost. In this case, the user should start with monitoring the writing capabilities of the disk and check its state. If everything is OK and hardware issues are not observed, the solution should be the same as mentioned previously.

There is one more case when such an error might appear. It is logical to assume that if some disk unexpectedly completely fails (local) or goes offline (network) this message will likely be the first thing the user notice in the logs.

"I/O error occurred".

This trivially means that Operating System returned a read/write error message to Nx Server on the command to read or write data block. Depending on the setup this message might pop up in pair with the previous one. It definitely tells the user that major issues are happening (e.g. the Operating System met the bad blocks, the drive is unexpectedly remounted to a read-only state or the network file system returned remote service inaccessibility).