SkyHawk vs WD Purple - Surveillance Drives Compared

The specifications are nearly identical, and that is the finding

Most comparisons of these two lines work hard to manufacture a winner. Read both makers' datasheets side by side and the honest result is that at the tier level they match almost exactly.

Seagate rates the standard SkyHawk line for always-on workloads of 180TB per year with a three-year limited warranty. Western Digital rates the standard WD Purple line at 180TB per year with a three-year limited warranty. Both state support for up to 64 cameras. Move up a tier and the symmetry holds: SkyHawk AI is 550TB per year with five years and 32 AI channels, and WD Purple Pro is 550TB per year with five years and 32 AI streams. These are not approximations of each other; they are the same numbers.

That symmetry is not a coincidence. Both lines are aimed at the same recorders, sold through the same channels, and specified against the same duty cycle, so they have converged. When two products converge on specification, the remaining differences are price, capacity availability and per-model detail — which is exactly what the live tables on this page compute and what a static specification comparison cannot.

So the recommendation is unusually simple, and we would rather say it plainly than dress it up: at a capacity where both lines are in stock in the same condition and the same tier, buy the cheaper one, after checking the recording badge. The delta table gives you that number today.

Where they genuinely differ: recording technology per model

The one specification that is not symmetric is the one that matters most in a recorder, and it favours Western Digital.

WD's current Purple data sheet and product brief state CMR explicitly for the current PURZ generation, and the Purple Pro brief states CMR for the models it covers. If you buy a current-generation Purple, the recording question is answered by the maker.

Seagate's position is more complicated. Its SkyHawk datasheet states SMR against ST4000VX013 in the same column block where the other 4TB part, ST4000VX007, is stated as CMR, and its SkyHawk SATA product manual repeats SMR for that generation including ST2000VX015. Seagate also publishes a separate CMR/SMR list stated by capacity rather than by part number, and that list shows no SMR anywhere in the SkyHawk line. Two Seagate documents say one thing at part-number resolution and a third says another at capacity resolution.

We do not resolve that. We badge the part numbers the datasheet and manual name, link all three sources, and mark everything else honestly. The practical effect for a buyer is that a SkyHawk purchase requires reading the badge on the specific row while a current-generation Purple purchase does not, and that is a real if narrow advantage to WD.

The asymmetry runs the other way on WD's older stock. The previous-generation WD Purple data sheet prints no recording-technology row at all, so those part numbers carry no claim from us and show as unverified. Neither line is uniformly documented; they are undocumented in different places.

The per-model detail both lines hide behind a tier name

Reading either line as a single product is the mistake that makes these purchases go wrong, and both makers make it easy to do.

On the Seagate side the tell is the part-number letter. Standard SkyHawk parts follow the ST-capacity-VX pattern and SkyHawk AI parts follow ST-capacity-VE. One letter separates a 180TB-per-year drive from a 550TB-per-year one, and a marketplace listing titled only 'Seagate SkyHawk surveillance' does not tell you which is in the box.

On the WD side the tell is the suffix: PURZ and PURX for the standard line, PURP for Pro. But WD adds a second layer that Seagate does not, and it is genuinely useful. The previous-generation Purple data sheet gives a per-model annualized workload rating rather than a line rating, and three parts in that generation — WD82PURZ, WD101PURZ and WD121PURZ — carry 360TB per year against 180 for the rest. Those are standard-line drives with double the rated workload of their siblings, which is a materially different product hiding under the same name.

That same sheet gives RPM per model, showing 7200 on those three parts and 5400 on the rest. Neither figure is a performance claim from us; they are what the sheet prints, and they are the kind of detail that disappears entirely when a line is described as one thing.

Our [SkyHawk hub](/skyhawk) carries the tier decoder built from these part numbers, with the source document linked on each row.

How to read the live delta table

The table above pairs the cheapest in-stock drive from each line at each capacity, and it applies two rules that most price comparisons do not.

The first is tier matching. SkyHawk AI is compared with Purple Pro and standard SkyHawk with standard Purple, because a 550TB-per-year drive and a 180TB-per-year drive are different products regardless of sharing a capacity. Pairing them would produce a gap that measures the tier difference and label it a brand difference.

The second is condition matching. Surveillance drives sell heavily through marketplace sellers, and at several capacities the buy box is a used listing. A used drive on one side against a new drive on the other produces a gap that measures the used discount, not the brands. Every row in the table is same-capacity, same-tier and same-condition, and the condition is badged so you can see which market you are looking at.

Rows that fail either test print nothing at all. That leaves a shorter table than a looser comparison would produce, and every row in it is a comparison you could actually act on.

One consequence worth expecting: the direction of the gap is not stable. In a supply-constrained market a capacity thins out on one side and the remaining sellers hold pricing power, so the line that is cheaper at 4TB may be dearer at 8TB in the same week. That is a real property of the market rather than noise in our data, and it is the reason this page computes rather than asserts.

Capacity reach, and the ceiling that decides some purchases outright

Where the two lines genuinely part company is at the top.

Seagate's current SkyHawk AI datasheet covers 20TB, 24TB and 32TB part numbers, and Seagate's recording-technology list places the 32TB SkyHawk AI under Mozaic HAMR CMR. We have a 32TB SkyHawk AI in tracked stock. Western Digital's Purple Pro brief describes capacities up to 26TB, and the largest Purple Pro in our tracked stock is 24TB.

For most buyers this is irrelevant, because most recorders cap out well below either figure. For long-retention projects it decides the purchase by itself: if the retention you need does not fit in the bays you have at 24TB, the question of which brand is cheaper never arises.

This is also where stale advice does the most damage. Guides still describe SkyHawk as topping out around 10TB and Purple as a 1TB-to-14TB range. Both descriptions predate the current lineup by several generations, and a wrong ceiling propagates directly into a wrong hardware plan — a project that would fit in four bays gets specified with eight.

Check your recorder's maximum supported drive capacity before buying up the range. That limit lives in the recorder's documentation rather than the drive's, and a drive above it may not be recognised at all.

What we deliberately do not claim

Comparisons of these two lines circulating online carry a striking amount of invented precision: percentage improvements in write performance, reliability figures attributed to nobody, and camera counts that appear in no datasheet. We repeat none of it, and the omission is the point rather than a gap.

Every specification on this page came from the maker's own datasheet for that exact part number, and the sources are linked. Where a datasheet did not state a field, the cell is a dash. Where a maker's own documents disagree with each other, we show both and say so. Where a figure is the maker's claim rather than a measurement — camera counts, AI channels, workload rates — it is attributed and reproduced in their terms rather than paraphrased into something firmer.

We also publish no performance comparison between these lines and carry no benchmark table. A recorder's constraint is sustained sequential write and the network in front of it, and the differences quoted between surveillance models rarely trace to a documented test at all. A number we cannot source would make this page look more authoritative and be worth less.

What we do have that a static comparison cannot is the price. Every figure in the tables was in stock when the page loaded, refreshed every few hours, condition badged, with out-of-stock rows excluded from the rankings entirely. The specifications belong to the makers; the arithmetic on today's prices is ours.

Our recommendation

At a capacity where both lines are in stock, in the same tier and the same condition, buy the cheaper one after checking the recording badge on that specific row. The published specifications are close to identical at both tiers, so paying a premium for either brand buys nothing the datasheets can justify. Buy SkyHawk AI specifically when you need capacity above the Purple Pro ceiling, and prefer a current-generation WD Purple when you want the recording question settled by the maker rather than by reading a part number.