There are many reasons an organization may want to retain video footage for a long period of time: OSHA recordable incidents, workers compensation claims, first report of incident (FROI) review, maintenance and operational reviews, theft or vandalism investigation, just to name a few. Depending on state, industry, or other corporate requirements, video retention may be required for anywhere from 90 days to 3 years. Long term video storage requires a lot of storage capacity, even with the newest H265 or ultra 265 codecs, adding up to tens or hundreds of terabytes of capacity required, with some organizations looking at petabyte scale storage requirements!
When considering an investment in video recording storage capacity, the importance of redundancy must not be forgotten. With no redundancy, a drive failure results in total loss of the contents of that drive, meaning that you have just lost the data that you invested so heavily in storing. RAID (Redundant Array of Independent Disks) storage requires at least one extra hard drive to provide parity and prevent data loss in the event of hard drive failure.
NVR devices with RAID storage require a RAID card to manage the array of disks. Not all RAID cards are the same, different RAID cards support different RAID levels, and special cards are needed to support nested RAID. There is no right answer for the “best” RAID array to choose, it is always a cost-benefit analysis to balance redundancy, performance, hardware cost, and uptime.
There are 7 standard RAID levels, and at least 6 nested RAID levels that utilize two or more standard RAID levels in combination. The most common RAID levels chosen for video storage are briefly discussed below.
RAID 0: striping without parity. This means that if any one of the drives in RAID 0 fails, the entire array fails and all data is lost. The benefits of RAID 0 storage are in read/write performance, and this RAID configuration is not recommended for video storage.
RAID 1: mirroring. This is the most basic form of RAID storage that provides redundancy. Every single hard drive in RAID 1 is an exact copy, which reduces maximum storage capacity to the size of the smallest drive in the array. So, (2) 1TB hard drives in RAID 1 has a maximum storage capacity of 1TB. Requires a minimum of (2) drives, but will remain operational as long as (1) drive is remaining.
RAID 5: block-level striping with distributed parity. A more complicated form of redundancy that allows the array to remain operational as long as no more than 1 drive fails. Requires a minimum of 3 drives. Reduces maximum storage capacity by (1) drive, so (3) 1TB hard drives in RAID 5 has a maximum storage capacity of 2TB.
RAID 6: block-level striping with double distributed parity. Similar to RAID 5, but allows the array to remain operational as long as no more than 2 drives fail. Requires a minimum of 4 drives. Reduces maximum storage capacity by (2) drives, so (4) 1TB hard drives in RAID 6 has a maximum storage capacity of 2TB.
RAID 10: striping and mirroring. Similar to RAID 1, in that storage capacity is significantly reduced, with an improvement to read/write performance. RAID 10 is actually (2) or more groups of RAID 1 storage in RAID 0 configuration. Requires a minimum of 4 drives. Reduces maximum storage capacity by at least one-half; a (4) 1TB hard drive configuration would have a maximum storage capacity of 2TB.
RAID 50: double block-level striping with parity. RAID 50 is (2) or more groups of RAID 5 storage in RAID 0 configuration. Requires a minimum of 6 drives. Reduces maximum storage capacity by one drive per RAID 5 group; a (6) 1TB hard drive configuration would have a maximum storage capacity of 4TB.
RAID 60: double block-level striping with double parity. RAID 60 is (2) or more groups of RAID 6 storage in RAID 0 configuration. Requires a minimum of 8 drives. Reduces maximum storage capacity by two drives per RAID 6 group; a (8) 1TB hard drive configuration would have a maximum storage capacity of 4TB.
As you can see, RAID storage is a complex topic, but it must be considered for any serious investment in data storage. RAID storage is a form of protection, like insurance, and it would be irresponsible to make a large investment without any sort of protection. Consult a professional to help select the optimal RAID storage level for your application and budget.
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