18 TB Enterprise HDD: Exos X18 or X20, Ultrastar, WD Gold and Toshiba

18 TB enterprise HDD prices: the Amazon.co.uk table

Prices are pounds sterling inc VAT. Right now the table holds 11 listings for enterprise-class drives. Lowest £/TB among tracked offers at the last check: £20.50/TB. Each row carries a Buy on Amazon button.

Drives from different generations can sit side by side here, and a cheaper row is not automatically the same drive for less. Start with the Part number column, then use the sections below to place it.

EAMR, FC-MAMR and CMR at 18 TB: what each sheet says

WD calls the HC550 the first HDD in the industry to harness Energy-Assisted Magnetic Recording, or EAMR, which it says improves writability and increases areal density. The same sheet also describes the drive as CMR. So on WD's own wording, EAMR is how the density goes up. It is not presented as an alternative to CMR. The density shows in the sheet: 1022 Gbits per square inch at 18 TB, against 918 at the HC550's 14 TB and 16 TB.

Toshiba frames it the same way. The MG09 overview says its 18 TB of CMR capacity is delivered using Flux Control Microwave Assisted Magnetic Recording, or FC-MAMR. The MG10 SATA overview makes the same statement of its 20 TB model and lists both CMR and FC-MAMR among the key features of its 20, 18 and 16 TB series.

Seagate's X18 and X20 sheets each mark Conventional Magnetic Recording as Yes for their models. We did not find a recording statement in the Gold sheet. For any row in the table, go by the Recording column: CMR in an Amazon title is the seller's wording, not evidence.

Seagate 18 TB enterprise HDDs: X18 or X20

18 TB is the top of the X18 sheet and the lower of two capacities on the X20 sheet. The X20 has the higher rate, 285 MB/s against 270 MB/s. It draws a little more at idle: 5.4 W against 5.3 W in SATA, and 5.8 W against 5.6 W in SAS.

What does 15 MB/s buy? Writing a whole 18 TB drive once, taken as 18,000,000 MB, takes at least 17.5 hours at 285 MB/s and 18.5 hours at 270 MB/s, by our own division. That is a best case at the top rate, with nothing else touching the drive, so treat it as a one-hour gap at most and not as a forecast for an array.

The X18 sheet also prints a 256 MB cache, 670 g, a 2,500,000 hour MTBF and a 5-year limited warranty for its new models. The generation pages at Exos X18 and Exos X20 take each across its other capacities.

18 TB part numbers from Seagate, WD and Toshiba

ST18000NM000J and ST18000NM000D look like near neighbours. The first is an X18 with SATA. The second is an X20 with SAS. Check the final letter and the interface together, because the digits settle neither.

WD 18 TB enterprise HDDs: Ultrastar HC550 against WD Gold

WD's case for this capacity is one of scale. It says the 18 TB HC550 gives 29% more capacity than the 14 TB HC530, and claims a data centre using 18 TB drives in place of 14 TB needs 22% fewer racks while using 21% less power per TB at idle. Those are WD's own figures. The rack claim also matches the plain sum, since 14 divided by 18 leaves about 22% fewer drives for the same total, so it says little about this drive beyond its size. It applies if you are building out racks. It is no reason to buy one drive.

The 18 TB is the fastest HC550 on the sheet, at 269 MB/s against 262 MB/s below it. WD Gold's WD181KRYZ is the smallest of the five models in the Gold sheet's first table, which runs 26, 24, 22, 20 and 18 TB. It matches the HC550's SATA model on all three figures in the table above, whereas the 26 TB Gold reaches 0.22 W/TB. So choose between them on what else you need, such as SAS or encryption, which the Gold sheet does not list. The range view is on WD Ultrastar.

Toshiba 18 TB enterprise internal hard drives: MG09 and MG10

Toshiba reaches the same 18 TB on two mechanical designs: nine disks on the MG09, ten on the MG10, both helium-sealed. The sector format does not follow the generation, because each series offers both. MG09ACA18TA and MG10ACA18TA are the 4Kn SATA models, and MG09ACA18TE and MG10ACA18TE the 512e ones. Only the MG09 adds SAS numbers in the overviews we hold, since Toshiba's MG10 SATA Series overview lists SATA models only.

Beyond the disk count, the two overviews print the same headline figures: 268 MiB/s, a 512 MiB buffer, 550 TB per year, a 2,500,000 hour MTTF and a 0.35% AFR. We have not found a Toshiba warranty length in the documents behind this page, so we print none for these drives. Later generations are on Toshiba MG series.

SAS listings at 18 TB, and what the X18 sheet changes for them

The SAS table holds 5 listings from the last price check, starting at £20.50/TB.

The X18 sheet lets you compare the two interfaces at one capacity with no generation in the way. SATA has a single port and SAS two. SAS adds 520 and 528 byte sectors beside 512. Under the sheet's random 4K test, maximum operating power is 9.4 W and 6.4 W for SATA, 9.8 W and 7.0 W for SAS. We name no compatible controller or backplane on this page, so check your own hardware's documents for the interface it takes. The SAS hard drives page is not limited to this capacity.

Seagate's two recertified 18 TB numbers, and the new listings

Seagate's Factory Recertified sheet names only two drives at 18 TB: ST18000NM002C and ST18000NM003C. Its 14 TB and 16 TB columns have three each, and the first row at 18 TB is a dash. The sheet states a 6-month limited warranty for these models, against the 5 years on the X18 sheet. If a seller describes an 18 TB drive as factory recertified, ask which of the two it is, because the listing's condition alone will not tell you.

The next table keeps to new condition and holds 10 listings, the lowest at £31.94/TB.