Eirsec CCTV recorders only use Seagate and Western Digital Hard drives which are designed specifically for CCTV recording purposes (24x7 recording) 

These hard drives are designed and optimized for digital video surveillance purposes enabling greater capacity, reliability and performance when compared to normal hard drives.

"Standard" hard drives are designed to be used in desktop or server computers and are designed to run for 8 hours a day, 5 days a week as a maximum work level.
However "CCTV grade" hard drives are rated for 24x7 use and are designed to withstand these intense work cycles while also providing increased performance when writing video footage. Additional benefits are seen from a CCTV grade HDD as they generate significantly less heat than standard drives. This is how Eirsec are able to provide fanless recorder units.

Older type hard drives would require more cooling fans and heatsinks to be made available within the DVR unit. Cooling fans were often large and usually too loud to allow a DVR to be placed in a living room or any place where noise would become a distraction. 

Read the Seagate "SV" Hard drive product overview here

Read the Seagate "SV" Hard drive Datasheet here

Key benefits and Features of CCTV grade Hard Drives

Increased performance when used in CCTV recorder applications.

• SATA interface enables increased video data rates (480 Mb/s)
• Optimized for recording of multiple, simultaneous video streams
• Seagate SV35 Series and WesternDigital Hard drive SATA interface enables multi-drive SDVRs with up to 3-Gb/s performance
• ATA-7 streaming commands allow data reads/writes to be tailored for increased video streaming performance.

Higher Reliability

• Designed for 24x7 operation and high write duty cycles
• >1 million hours MTBF in 24x7 video surveillance applications
• Capable of operating under drive case temperatures of up to 75ºC
• Lower power consumption and reduced heat generation

Tailored for the video surveillance industry

• Technical and marketing support infrastructure dedicated to video surveillance customers
• Fifth-generation SV35 Series drives and green rated Western Digital HDDs dedicated to evolve with emerging video surveillance industry requirements