Reviving an old thread, as I have comparable needs.
(disclaimer: I have a background of large scale video processing and storage)
With video storage, if you do 24/7, or if you have many events or many cams, it is important to look at the disk specs in detail. Focus on disks where you can find the Workload Rate (TB/year) or TBW (or DWPD).
By the way, if anyone can find those numbers for consumer Barracuda 2.5 or Firecuda 2.5, I would be interested.
Examples (no guarantees here, see manufacturer specs for reference):
- Consumer level regular disks (Barracuda) are for about 110 TBW (55TB/yr for 2 yrs), no matter the capacity of the disk, and probably also no matter the size factor.
- Consumer level NAS disks (WD Red, Ironwolf, WD Purple) are for about 540 TBW (180TB/yr for 3 yrs), no matter the capacity of the disk, or the size factor.
- a bit more Pro NAS disks (Ironwolf Pro and Barracuda Pro) 10/12TB are for about 1500 TBW (300TB/yr for 5 yrs), or 2750 TBW for WD Gold.
- Samsung 850 Pro 4TB has about 600 TBW
- Intel DC S3610 1.6TB goes to 10700 TBW
In general: recent prosumer NAS and enterprise disks have published numbers that are fairly reliable. On somewhat older disks (Enterprise WD Re series for example), I have found that the given numbers were very 'optimistic'. I haven't tested HGST Ultrastar He drives, I find the way they published their max workload rate a bit 'light'.
It is tempting to go for the high capacity drives in order to reduce the number of disks, but since they only support so many writes, you may need to replace them sooner than you would with the load spread out over more disks. The TCO may be more interesting with lower capacity disks, even if you need to buy more of them to get to your desired capacity.
Also, for your TCO, take power consumption into account, as it can be anywhere between 1% and 70% of your procurement cost (yes, it varies that much).
Enterprise disks consume a lot more than consumer disks in general, and the lowest consumption figures can be found with 2.5" disks (but you may need a lot of them). What surprised me when I started looking into SSDs for this purpose was the extremely high TCO of SSDs, both in purchase cost and power consumption (because you will need a lot of them).
Now for some conclusions:
The number given of 1TB/week is about 13Mbps. Add indexes, and you go to something like 20Mbps raw.
If you want to use 24/7 good quality 2Mpixel or more with a not too low fps, you will need about 8-15Mbps per camera, depending on the encoding and the image noise (depending on lighting, scene, and sensor quality). For 15 cameras that would mean 100-200Mbps total. 1 month of video would mean 32 to 65TB.
(side note: you'll be surprised how useful 24/7 recording combined with some GOOD motion detection software is, especially if that software is multi-camera aware.)
So I will give some numbers I compiled, as there are a lot of variables.
Example of lowest TCO solutions I have found for consumer and prosumer grade disks (when using RAID with some level of redundancy, plus a bit of headroom):
- 10TB, up to about 50Mbps, 24/7: WD Purple 6TB. Budget: about 650EUR for 5yrs. Do not lower the number of disks and take the higher capacity 10TB+ disks, you will need to replace them before the 5 years, they risk going over their write capacity. And lower capacity drives will be more expensive overall.
- 10TB, 100Mbps, 24/7: WD Purple 3TB . Budget: about 740EUR for 5yrs. Almost all higher capacity disks will go over their write capacity, or will be more expensive.
- 20TB, up to 100Mbps, 24/7: WD Purple 6TB. Budget: about 1300EUR for 5yrs
- 65TB, 200Mbps, 24/7: WD Purple 8TB . Budget: about 4100EUR for 5yrs
2.5" disks are almost never economical on higher capacity and bandwidth needs. I've had some good experiences with the now defunct 2.5" WD AV range, but that was on lower needs.
This list was compiled by comparing the disks mentioned above in the TBW list.
Close contender to WD Purple is WD Red, and Ironwolf in some very limited cases. In some high capacity/high load cases WD Gold is a contender.
And yes, I stretch those 2 or 3 year disks out to 5 years. The above calculations are just based on max write load. I do however recommend using 5 year guaranteed disks, as peace of mind is also worth something. Try to buy through recommended channels though, some manufacturers have fine print you'll be surprised about.
The speed of the disks is rarely an issue (be it IOPS or MBw/s), provided the indexing and the writing is done with some care, which usually is the case with NVRs. With this usage profile (sustained sequential writes, write heavy), caching on flash or a ZIL on flash (be it SSD/NVMe/Optane) is not only of NO use, you will even burn through your flash in no time.
(my 2 cents, no guarantees implied)
