Redundancy; Cables; Raid - Vivotek IP Surveillance Overview

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Chap.6 Bandwidth and Storage

DAS

Images are transmitted from a camera to a host PC via Ethernet cables and stored directly in the hard disk drive of

the PC. DAS is aimed to enable storage and playback on the same PC and is mainly used by small- or medium-

sized businesses.

NAS

Images are transmitted to a purpose-built NAS server via Ethernet cables for storage. NAS allows storage and

playback on different platforms and is especially suitable for enterprises that need to access and share large-

volume data

SAN

Images are sent to a purpose-built SAN server via an exclusive fiber optic cable for storage. As with NAS, storage

and playback of images can be performed on different platforms, but SAN further reduces Ethernet bandwidth

usage and offers a faster transfer rate.

6.3 Redundancy

In a bid to avoid significant losses from network downtime and hard disk drive cracks, it is highly recommended to

plan a redundancy solution ahead, such as using back-up cables or RAID structure.

Additional cables can be deployed during installation for failover. When the trunk cable is out of order, system will

switch over to the redundant cable to avoid system downtime.

RAID (Redundant Array of Independent Disks) is an array of several hard disk drives that can be used as one

single hard disk drive. Data can be spanned over multiple disk drives under one system. If one of the drives cracks,

the data can still be recovered.

The only difference between RAID and a hard disk drive is their array structure. Compared with a large-volume

hard disk drive, RAID provides higher reading/writing speed, stronger data integration, redundancy and processing

capability and better recovery capability.

RAID 0 (Striped)

With RAID 0, data is split into several segments and written to individual hard disk drives sequentially. For example,

256k data is split into four 64k segments and written to four hard disk drives.

RAID 0 can deliver better I/O performance and faster reading and writing speed. However, if one of the hard disks

cracks or if any problem occurs, all data will be destroyed.

RAID 1 (Mirrored)

RAID 1 writes data simultaneously into two disk drives, one with the original data and the other with the duplicated

copy. When one of the disk drives is out of order, users can still retrieve data from the other drive.

RAID 1 offers faster reading speed and better data; however, an additional drive must be added to store replicated

data, thereby increasing installation costs.

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