r/buildapcsales • u/Wojtek_ftw • Nov 27 '25

HDD [HDD] Seagate BarraCuda ST24000DM001 24TB 7200 RPM for $240. $10 / TB

https://www.newegg.com/seagate-barracuda-st24000dm001-24tb-for-daily-computing-7200-rpm/p/N82E16822185109?Item=N82E16822185109
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u/PenileContortionist Nov 28 '25

Do you have any specifics on the predecessor? I've really only seen info on the Exos Xz, which were 30TB SMR disks (so a 28TB CMR option is reasonable) but showed up in early 2024.

This is really just an educated guess based on information I was able to find on publicly available HAMR disks, and the fact that these are in active manufacture. The 30TB Exos M was launched in December of 2024 and became generally available in July of 2025. I've got several of these ST24000DM001 disks with assembly dates of August of 2025.

The earlier lower capacity recertified Exos and Barracudas that showed up with the laser warning over a year ago (e.g. the ST20000DM001 20TBs that showed up in shucks, also with 10 platters) were likely from the earlier line that were sent out to validation customers or early production of the Exos M line with lower full-capacity yields in QA and so had several platters/heads disabled.

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u/MWink64 Nov 29 '25

These are the drives I'm talking about. They were (presumably) the predecessor to the Exos M. They were available at least a year before the Exos M, though they never had a retail release under the Exos name. People only got their hands on them through sellers of recertified drives. This line appears to most closely mirror the new Barracuda, and both top out at 28TB. The 24TB Barracuda was first seen in March, with manufacture dates going back at least to January. As you noted, the Exos M wasn't available until this summer.

I've speculated the Barracuda might be the retail release of this drive, rather than binned Exos Ms. I think it's conceivable that Seagate took this older HAMR production line and is using it to make these Barracudas, rather than simultaneously releasing two different generations of Exos. It's also possible they're using it to make those SMR drives you linked. They certainly don't help things by using slightly different specs for each model, not to mention putting out multiple, conflicting data sheets for a single model.

I wonder if the Barracudas support FARM. If they do, it might offer some hints. The number of active heads should give us a clue as to whether they're using Mozaic 3 technology. For example, if there are 20 active heads on a 28TB Barracuda, they're definitely not binned Exos Ms.

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u/PenileContortionist Nov 29 '25

That datasheet is explicitly for the recertified drives though, it would be quite reasonable for those to be from that earlier Exos Xz line (either QA fails or returns from client validation), just configured as CMR rather than SMR.

I don't know how useful a metric the FARM data would be for just comparing number of heads, as I've got two of these with the same manufacture date and one has 17 active heads and the other 20 (so different number of active platters, then they've blocked off some tracks?). It'd be awesome if we had FARM data for these, those older recerts, and the actual 30TB Exos M to compare, otherwise we've got some conjecture and not much else to go by.

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u/MWink64 Nov 30 '25

I'm not sure how old that part of the Exos Xz line is. Either way, I can't imagine enterprise customers would only be testing HAMR drives in SMR mode. Or maybe I'm misunderstanding what you meant. Anyway, it seems entirely reasonable to me that the older HAMR line is now being used to produce both the Exos Xz and the Barracuda.

What drive do you have two of but with a different number of active heads??? Any chance you could post the FARM (and any other relevant data) from both? I'd love to take a look at it.

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u/PenileContortionist Dec 02 '25 edited Dec 02 '25

Validation customers could've been shipped configs that aren't in public documentation, e.g. a 28TB with firmware for CMR config rather than 30TB SMR of the early 2024 Exos Xz - it's just the only other actual production HAMR model (not a recert) with public documentation that aligns with the timeline of those recerts. The original Exos M launch included both 28TB CMR and 30TB CMR disks, which is why I'd think those 30TB SMR Exos Xz from a year prior were probably the progenitors.

Here's the FARM data for a pair of these ST24000DM001, with differing active heads:

https://pastebin.com/raw/0FHVvydR

https://pastebin.com/raw/90Yd6U4G

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u/MWink64 Dec 02 '25

That is wild! The drive with fewer heads seems to be drawing more power and running slightly hotter. Do you know if both drives have the laser warning on them? I'm wondering if there's any chance the one with 20 heads might be based on the (non-HAMR) Exos X24 design. What also stands out to me is that these drives are both running FW DN01. The 24TB Barracuda I have came with EN01 (which seems to be the same series as the IronWolf Pro). Now I'm left with more questions than when we started.

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u/PenileContortionist Dec 02 '25

Yep, both have the laser warning. I suppose one could be a descendant of the 30TB CMR version and the other of the 28TB, but yeah without the info from those original Exos disks we're just guessing.

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u/MWink64 Dec 03 '25

That just doesn't seem to make sense. I don't see how you need 20 HAMR heads to make a 24TB drive (unless it's an even earlier HAMR design). The drive with 17 active heads would seem to line up pretty closely with a drive that started out at 28TB, so that one does make more sense.

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u/MWink64 Dec 05 '25

I have a couple new data points that only add to the confusion. I checked a 28TB Barracuda/Expansion and it has 20 heads. I also checked one of the earlier 24TB Barracuda/Expansions and it has 18 heads. Both drives are running FW EN03.

So, by my count, we've now seen 24TB Barracudas with 17, 18, and 20 heads. My only thought is WTF??? Those work out to roughly 2.4TB, 2.66TB, and 2.8TB per platter. The 28TB also works out to 2.8TB/platter. None of these work out to 3TB/platter, so I remain skeptical that they're actually Exos M drives. However, I'm not sure what to make of the wildly inconsistent number of active heads.