RAID (Redundant Array of Independent Disks) storage allows for one or more redundant disk drives to be used in a computer, DVR (digital video recorder), NVR (network video recorder), NAS (network attached storage), or other types of servers so that data is not completely lost if and when a drive fails.
There are two types of hard disk drives (HDDs): those which have failed, and those which are going to fail. It’s inevitable: a hard drive can fail next week, next month, or in 10 years, but at some point, it will fail. RAID prevents this inevitable hardware failure to secure data by recording to a redundant disk drive within the RAID array, or the set of disks connected to a RAID controller.
There are numerous types of RAID arrays, the most popular of which are RAID-0 (data is written partially on one drive and partially to another for increased performance without any redundancy meaning if one drive fails, then the entire array is lost), RAID-1 (two mirrored drives), RAID-5 (one drive can fail without losing data), RAID-6 (two drives can fail without losing data), and RAID-10 (a combination of RAID-1 and RAID 0 for increased performance and redundancy).
A hot-spare is a nice touch in any type of system where user intervention is not possible to physically replace the failed drive with a new drive, or if the system is to be kept online and operational without any downtime. Hot-spares are spare drives in an array that will immediately take the place of a failed drive. The system stays online and automatically replaces the failed drive and starts to rebuild the array. It is important to note that the failed drive should be replaced immediately or as soon as possible, because if another drive within the array fails, then all data can possibly be lost unless using a dual-parity RAID such as RAID-6.
There are software-based and hardware-based RAID controllers, the latter being the more reliable, offering better performance, and costing substantially more money. Hardware RAID controllers typically have the option for battery backup, which allows for safe shutdown of RAID systems in the event of power loss. Software RAID controllers are typically installed on a motherboard.
More information about RAID can be found here.
The most common RAID scenarios in video surveillance applications are RAID-1 for the C drive or operating system, RAID-5 for the storage array, and RAID-10 if a performance enhancement is required, usually for higher-throughput applications.
At Custom Video Security, we build customized Windows-based servers for video surveillance applications, specifically for hosting VMSes such as Milestone XProtect, Digital Watchdog IP VMS, and more. Our NVR servers are professionally designed with hardware-based RAID controllers with the ability for creating multiple arrays on each RAID card. For example, if a server has 16 pcs drive bays, then we would typically use two highly reliable SSDs in mirrored RAID-1 format for the C drive. And the remaining drive bays would be loaded with surveillance-grade 5400 RPM SATA drives that are rated to handle the throughput stated in the server calculation, or enterprise-grade 7200 RPM SAS drives, in RAID-5 format with hot-spare. In certain circumstances where the server throughput is high, we would add a short-term live database in RAID-10 format using 15K RPM SAS drives. All of our redundant servers typically offer redundant power supplies and redundant video cards as well.
While using the latest technology is good and great in preventing data failure which can be catastrophic to any organization, it requires a higher budget and is only generally used for video surveillance in machines with higher camera count or long-term storage needs.
So what can be done as a low-cost alternative to using a hardware-based RAID solution? Here are a number of ideas:
1) NAS drive to export long-term storage. (NAS storage is typically not nearly as fast or reliable as internal or DAS: direct-attached storage, but offer the ability for numerous network devices to record to it.)
2) JBOD storage arrays, or DAS–connected directly via MiniSAS or similar cable for a high-performance, expandable alternative to NAS (only allows storage for the machine that is connected to it.
3) Cloud-based recording to upload a substream (lower resolution, lower frame-rate) recording. This is a paid subscription, which generally costs around $1 per day per camera.
4) FTP upload. (This is essentially a file server that is connected to the Internet, e.g. at the main office, and you can have multiple NVRs writing backup files to it. The problem is that at some point the FTP server will get full and files will have to be manually deleted before it gets full. Additionally, the Internet connection would have to be fast enough to handle the upload of the data at each site, as well as the download of the multiple streams of data at the main site.)
5) Software RAID. While we use hardware RAID for our PC servers, all of our Uniview NVRs ending in part number -B support redundant recording, which mimics a software RAID. Some of these part numbers include:
NVR308-64R-B (This is the only true hardware RAID machine, which is ideal for using any number of hard drives up to 8 pcs internally to create various RAID options.)
You can enable it here：
And you would just add a second drive and set it to redundant as shown here:
Please contact one of our security professionals at sales@CustomVideoSecurity.com with your project details if you require a redundant NVR or additional information on performance, cost, and benefit analyses on any of the alternatives listed here.