Surveillance hard drives
Drives tuned for continuous writing from cameras, which is close to the opposite of a desktop workload.
A recorder writes many streams at once, all day, and almost never reads them back. Drives built for it favour sustained sequential writing and tolerate a much higher workload rate than a desktop drive is rated for. That is why a surveillance drive can look unremarkable on paper and still be the right one for the job.
What an ordinary surveillance drive looks like
| Capacity | 3.9 TB |
| Cache | 64 MB |
| Price per terabyte | $40–60 per TB |
Medians, with values beyond 1.5× the interquartile range excluded so one listing cannot move them. A class holding fewer than 8 drives publishes no baseline at all.
How this class is distributed
49 drives in this corpus sit in this class. By capacity:
| Under 2 TB | 14 |
| 2 TB to 4 TB | 13 |
| 4 TB to 8 TB | 10 |
| 8 TB to 14 TB | 7 |
| 14 TB and above | 5 |
The only class here that deliberately spins slower
Almost every drive in this corpus turns at the same speed, and surveillance drives are the visible exception: they cluster lower. That is a design decision rather than a compromise. A recorder writes several video streams continuously and reads almost nothing back, so sequential write endurance matters and seek performance does not. A slower spindle runs cooler, draws less power and lasts longer under a duty cycle that never stops, and the throughput lost is throughput this workload was never going to use.
Written to constantly, read from almost never
This is the inverse of a desktop workload and it changes which specifications matter. The figure to look for is the number of simultaneous streams the drive is rated for, which manufacturers publish and listings often omit. Capacity then follows arithmetic rather than preference: stream bitrate multiplied by camera count multiplied by retention days. Most buyers arrive at a capacity by guessing and discover the recorder overwriting footage sooner than expected.
Why a desktop drive fails at this job slowly
A desktop drive put in a recorder will work, and will keep working for a while. What it is not rated for is writing continuously for years, and the failure is gradual rather than sudden — dropped frames, then a drive that reports errors, then footage that is not there when it is finally needed. The cost of finding out is asymmetric: the drive is the cheapest part of the system and the recording is the entire point of it.
Where this class sits on price
Surveillance drives are not the cheapest per terabyte here, and they sit in the middle capacities rather than the largest. That is worth knowing because the temptation in a camera system is to buy the cheapest bulk storage available, and the cheapest per terabyte in this corpus is an enterprise drive that is rated for a different job and will be louder doing this one.
Shingled recording, and the word that is missing
Drives record in one of two ways. Conventional recording writes tracks side by side; shingled recording overlaps them like roof tiles to fit more on a platter, which makes rewriting a track require rewriting its neighbours. On sustained writes a shingled drive can slow to a fraction of its rated speed once its cache fills, and in a RAID rebuild that can turn hours into days. The tell is what listings choose to say: in this corpus the term CMR appears roughly twenty times more often than SMR, because conventional recording is advertised as a feature and shingled recording is simply not mentioned. Silence is not evidence of either, but a drive that makes a point of saying CMR is telling you something a drive that says nothing is not.
Recertified and renewed listings
Roughly one listing in seven here is sold as recertified, renewed or manufacturer-refurbished. These are drives that have been returned or pulled from service, tested and resold, and they are usually the cheapest per terabyte on the page. What changes is the warranty — often months rather than years — and what is not disclosed is the hours already on the drive. For storage where the data exists elsewhere, the arithmetic can be sound. For the only copy of anything, buying a drive with an unknown history to save a fraction of its price is a poor trade, and the price per terabyte on this page does not distinguish between the two.
Why the capacity you get is smaller than the one you bought
Drive manufacturers count a terabyte as a trillion bytes; operating systems generally count it as 2^40, about ten per cent more. A 4 TB drive therefore shows as roughly 3.63 TB before a single file is written, and nothing is wrong. Formatting and the file system take a further small share. This is not a specification any listing states and it is the most common reason a new drive appears to have arrived short, so it is worth expecting rather than discovering.
Working out the capacity you need
The arithmetic is bitrate multiplied by cameras multiplied by retention, and it is worth doing before choosing a drive. A single 1080p stream at a moderate bitrate consumes on the order of a few hundred gigabytes a month; eight cameras at that rate fill several terabytes in the same period, and thirty days of retention is a common requirement. Motion-triggered recording reduces it substantially and unpredictably, which is why a margin matters. Buying the capacity that the arithmetic gives and then adding a class is cheaper than discovering in six months that the footage that mattered was overwritten last week.
Warranty against a duty cycle that never stops
Surveillance drives carry warranties in the middle of this corpus, shorter than NAS and enterprise drives despite running just as continuously. The reason is the workload rather than the hours: writing a steady stream of video sequentially is gentler on a drive than the mixed random access an array serves, so the manufacturer prices the cover accordingly. It is worth checking against the recorder’s expected life, because a camera system is usually installed once and left, and a drive that outlasts its warranty by years is the normal outcome rather than a lucky one.
Reading these figures
Every number above is a median of what manufacturers publish, not a measurement we took. Where a specification is missing from this table it is because too few listings in the class stated it for a median to mean anything — that is a fact about the listings, not about the drives.
Narrow this class by capacity and budget in the hard drive finder.