Disk storage subsystem requirements

General requirements

For C-Werk VMS operation, the disk subsystem should match the following requirements:

1. The number of input/output operations (IOPS) of the device should not be less than the IOPS of C-Werk VMS.
   C-Werk records the archive in blocks of 4 MB every 10 seconds. However, if the block is not filled in 10 seconds, a smaller fragment of the block will be recorded, which will be added to later.
   Archive playback is also performed in blocks (except when reindexing, see Console utility for working with archives).

   Below you can see how you can estimate the IOPS for C-Werk VMS.

   	If the average bitrate per camera is less than ~3.6 Mbps	If the average bitrate per camera exceeds ~3.6 Mbps
   IOPS during archive recording Archive recording includes both data input (recording) and output (reading) operations	IOPS (recording) = 0.29 * N IOPS (reading) = 0.035 * M	IOPS (recording) = 0.065 * M IOPS (reading) = 0.035 * M
   IOPS during archive playback Archive playback includes only output (reading) operations	IOPS (reading) = 0.035 * R * S
   IOPS during simultaneous recording and playback	IOPS (recording) = 0.29 * N IOPS (reading) = 0.035 * M + 0.035 * R * S	IOPS (recording) = 0.065 * M IOPS (reading) = 0.035 * M + 0.035 * R * S
   where N is the number of cameras being recorded; M is the cumulative bitrate of all cameras being recorded, in Mbps; R is the cumulative bitrate of all cameras being played back from the archive at normal speed (1x), in Mbps; S is the playback speed.

2. If you use RAID storage, specify the write-back policy for recording to cash memory.

Storage requirements

The disk subsystem capacity of C-Werk Server should be estimated taking into account the resolution, the compression algorithm, the frame rate of the recorded video signal, the number of video cameras from which the recording to disk(s) takes place and other recording parameters. In addition, the size of the system log and metadata databases should be considered.

Minimum requirements

You need at least 10 GB of free disk space on Windows OS and 5 GB on Linux OS to install the C-Werk VMS package in the Server and Client configuration.

See the storage calculations below, taking into account the size of the archive, the size of the database and the size of the archive of the system logs.

Size of the archive

The capacity of the disk subsystem can be calculated by the formula:

Capacity of disk subsystem (MB) = Time of storing archive (days) * Cameras number * Rate of recording (FPS) * 3.51 * Time of guaranteed recording from a camera (h/day) * Average frame size (KB),

where

Time of storing archive is the required time for storing an archive from one camera, days;

Cameras number is the number of cameras from which recording to the archive takes place;

Rate of recording is the frame rate of recording to the archive, frames per second;

3.51 = (60 sec in min * 60 min in hour) / (1024 KB in MB) is the factor used for KB/s in MB/h conversion;

Time of guaranteed recording from a camera is the number of hours of guaranteed recording from one camera per day;

Average frame size is the average size of the camera frame in KB.

Examples of calculating the capacity of the disk subsystem (without the capacity of the system log and metadata databases) are presented below.

System log database

The capacity of the system log database should be taken into account when the capacity of the disk subsystem is calculated. The estimated capacity of the system log database is calculated by the formulas:

Capacity of system log database (low detection tools activity) = D * T * (0.04 GB / day);

Capacity of system log database (average detection tools activity) = D * T * (0.12 GB / day);

Capacity of system log database (high detection tools activity) = D * T * (0.48 GB / day);

where 

D is the total number of detection tools created in the system,

T is the estimated duration of system log storage, days.

Metadata database 

The following formulas can be used to determine the required disk size for the metadata database:

Size of metadata database = N * T * (0.5 GB / day) – sufficient disk size;

Size of metadata database = N * T * (1 GB / day) – sufficient disk size plus reserve space;

Size of metadata database = N * T * (5 GB / day) – sufficient disk size plus a large reserve,

where

N is the number of detection tools in the system actively recording metadata. One video camera can have several detection tools with metadata (see General information on metadata),

T is the period of time (number of days) that metadata will be stored. By default, T = 30 days.

If you have less than 15 GB of free disk space, the metadata database is overwritten - the new data is written over the oldest data.

The system logs

When calculating the disk subsystem capacity, it is necessary to include at least 1 GB for the system logs archive.

Self-diagnostics service

When calculating disk subsystem capacity, note that self-diagnostics service may generate up to 100 MB of data per day.

The depth of the service internal database is limited to 7 days and 512 MB.