When selecting storage for an IP surveillance system, there are four standard options: internal / direct-attached storage (DAS), network-attached storage (NAS), storage area networks (SAN), and on-camera edge storage. All of these have a place in surveillance applications, with different manufacturers supporting different options. In order to find out what integrators truly prefer, however, we asked the following question as part of our Winter 2012 survey:
Before we examine integrator favorites, let's review the terms / types:
- Direct-Attached Storage (DAS): Direct-attached storage is as it sounds, storage attached directly to the server, either internal to the server or external. Common protocols include SATA (and eSATA), SCSI, and SAS. Direct-attached storage is most often used when a single DVR/NVR or server is used for recording, with internal drives. If a longer retention period is needed, eSATA or SCSI expansion units are used.
- Network-Attached Storage (NAS): Network-attached storage consists of an appliance loaded with a hard drive or hard drives, which resides on the network, not attached directly to the recorder. The NAS's drive or drives may be mounted as network drives, though some NASs actually provide iSCSI services, acting as a SAN, as well.
- Storage Area Network (SAN): The term SAN refers to more than just a storage unit, but this use has been commonly accepted. A SAN is a network, either dedicated or shared, which is used for the transmission of storage data. It differs from NAS in that a NAS device contains an operating system, and may perform other functions, while a SAN is simply used for raw storage. iSCSI is the most common SAN protocol. SANs are most often used when multiple recording servers are used, since they are typically extremely scalable, sometimes in the petabyte range. This makes data from multiple recorders stored on a single SAN simpler to manage than individual drives in numerous servers.
- Edge Storage: This method refers to storage contained in the camera itself, either on flash or hard drive storage. This is not commonly used today but is seen by many as a potential big future option.