On the other hand, DAS may appear to be faster than any other storage method. Since it needs to transfer the data over the network, all the data will be transferred on a dedicated connection between the server and the storage device. However, due to the high speed connection of the Fiber Channel, in some cases SAN offers a higher speed compared to the speed provided by DAS. Also, because SAN separates storage from servers and consolidates them into a location accessible through any application, it offers better storage flexibility, availability and performance compared to DAS for large enterprises. Therefore, due to the enhanced SAN storage performance, organizations will not need additional storage devices, which saves money, although SAN devices can be costly. Moreover, separating the storage device from the servers allows the computing resources on the servers to perform other tasks not related to storage.
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On the other hand, the difference between DAS and Network Attached Storage (NAS) is that a DAS device communicates directly with a server without a network connection. DAS provides good performance, but there are limitations such as the number of servers it can access. DAS storage must be located near the server on the same shelf. The advantage of NAS over DAS is that it simplifies sharing files between multiple users. The main difference is how the computer or server handles a specific volume. If the server processor were responsible for managing the attached storage, it would be a kind of DAS and if the computer or server treats the attached storage like another computer, sharing its data over the network, it's a NAS.
Using Storage Servers for NVR and DVR:
Video surveillance requirements for high storage capacity and increased retention period, make the NVR or DVR to take advantage of external storage servers in order to achieve the required surveillance system. Regardless of the format, both DVRs and DVRs can use the external storage units provided in the previous sections to improve capacity and reliability.
The DAS was the most widely used storage device in digital video recorders, so it has generally become part of this recording system. For medium and large scale video surveillance where performance, reliability and scalability of a storage system are important issues, newer external storage such as SAN and NAS are more beneficial than DAS fixed storage.
Summary:
The storage component may be fixed internal DAS storage, or it may use some type of external storage. Also, the other major component of the surveillance system is the DVR or NVR which as the drive for the whole system manages one or more cameras and storage subsystem. The video frames from the cameras are transferred from the DVR or NVR to the storage system. So choosing the right storage device to achieve capacity and reliability leads to a great monitoring system.
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