Option 1: expand storage of existing DVR
Many enterprise-class security DVRs support storage arrays to expand the storage for each device. These are costly, but would work with no configuration changes.
http://www.techcctv.com/cat42_1.html
Option 2: Connect DVR directly to SAN device
Some DVRs supports the connection to an industry-standard SAN device.
This allows high-speed data connection directly to the SAN via iSCSI or Fiber Channel. This would work, for example, if the DVR runs Windows as the underlying OS, or the DVR vendor supports it. This would require a iScsi or Fiber Channel adapter in the DVR, and the purchase of the SAN device itself, if one does not exist as part of your IT infrastructure.
This would cost a lot, but would be the most reliable and the easiest to manage.
Both of the above solutions would require no change in operations; data would just get written to the DVR.
Option 3: NAS solution
NAS is a similar solution, but you're using the LAN for that access. NAS devices would be separate and apart from the DVR, and access would not be nearly as fast.
In most cases a NAS is not fast enough to use as a real-time storage medium for a DVR, and it creates other issues, such as security and possible lack of audit trail.
And it would likely require some manual copying or scripted backup to archive excess video data. But it would be much much cheaper.
For example, below is a 45TB NAS unit:
http://www.pcmag.com/article2/0,2817,2374637,00.asp
Option 4: Exhange your DVRs for NVRs
NVR video recorders are designed to record data to a SAN or NAS. Some NAS devices have NVRs built into the device.
http://www.intransa.com/
