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How Does DW Spectrum Manage Storage?

How DW Spectrum® IPVMS Manages Storage


Affected Roles:  Administrator, Owner

Related Digital Watchdog VMS Apps:  DW Spectrum® IPVMS

Last Edit:  March 16, 2021


Supported/Affected Devices:

  • DW Blackjack® Server Series
  • DW Blackjack® NAS Series
  • DW Blackjack® MINI™ Series
  • MEGApix® CaaS™ Series

Drive Detection & Use

  • The DW Spectrum® Server application, once installed onto a computer, detects and analyzes available storage during the setup process.
  • DW Spectrum® will utilize all drives that are installed within a Server and writes concurrently to all enabled drives.  As a result, the more drives that are in a Server, the less throughput you will see on any individual drive as the work will be shared across the enabled drives
  • DW Spectrum® will not allow recording to drives that are less than 10% the size of the largest drive in the system (e.g. an SD Card or USB Flash drive).  For example, if a user has a 10 TB NAS registered at a server, then all other drives with a total space that is less than 1 TB will be disabled for recording at the server.  This is done to ensure a correct write-ratio calculation and to improve overall system stability

Direct-attached Storage (DAS) Limitations

Direct-attached Storage (DAS) of external storage devices, such as external hard drives or solid state drives, are not supported by DW Spectrum® IPVMS.  Main protocols used for DAS connections are ATA, SATA, eSATA, NVMe, SCSI, SAS, USB, USB 3.0, and IEEE 1294.

While DW Spectrum® is capable of detecting the storage, just like the computer’s operating system, it is not supported as an official method of storage and may cause storage issues if it is implemented as a media drive for the Server. 

If external storage is necessary, Network Attached Storage (NAS) SMB storage is recommended instead.

General DW Spectrum® Write-to-Archive Process

  1. IP camera video streams are detected and captured by the DW Spectrum® Media Server and stored in RAM.
  2. The DW Spectrum® Server writes captured IP video in Ram to available storage (internal hard drives or NAS) once per minute.
  3. All suitable drives are written concurrently and the system calculates for their size according to a ratio.  For example, if a single Server has multiple hard drives of varying sizes, DW Spectrum® will fill up each hard drive at the the same rate to ensure that no individual drive’s system bus is overloaded.
  4. DW Spectrum® keeps some space reserved on every drive so that performance is not affected while archiving.
  5. When any storage drive is full, DW Spectrum® will begin to delete recorded video starting with the earliest/oldest video on the Server across all of the drives until there is enough space to record a given amount of data.  This is done while DW Spectrum® archives video to its media storage.  As a result, a solid Timeline can be maintained.
  6. Since the release of DW Spectrum® v2.6, recording to the Server computer’s OS drive is prevented as long as there are any other storage drives installed on the Server that met the minimum requirements and is at least five (5) times larger than the OS drive.
  7. The User cannot manually modify the archive (delete/add/etc.) through the DW Spectrum® Software

How Hard Disk Failure Is Managed

If a single drive in a multiple drive system fails, the DW Spectrum® system will do the following:

  • Continue writing to all of the remaining available drives
  • Create a notification in the DW Spectrum® Client’s Notifications panel to inform Administrators that a drive failure has occurred
  • Rebuild the archive index after the Media Server has restarted
  • If the Failover-on-Hard-Drive-Failure is enabled, then the cameras that were writing to the failed drive will begin to record to the next designated failover server (v4.0 and up)
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  • 16-Mar-2021