20TB SAS Drive: Seagate, Ultrastar and Toshiba Part Numbers, and the Controller Rule

20TB SAS hdd part numbers, SATA beside SAS

Read the last letter carefully. ST20000NM007D is the X20 in SATA, whereas ST20000NM007H is the X24-generation drive in SAS, so a single character changes both the generation and the interface. The portfolio sheet coded 2512, with a 2025 copyright, carries the H numbers, and Seagate's DS2080-2307US sheet labels them Exos X24. The factory recertified sheet adds near-matches in its SATA 6 Gb/s table: ST20000NM004C, plus ST20000NM002C and ST20000NM003C, which differ by one letter from the X20 SAS numbers ST20000NM002D and ST20000NM003D.

Toshiba needs the same care by generation. Its MG10 overview lists 20 TB as SATA-3.3 models only, while MG11 has a SAS model at this size, MG11SCA20TE. A Toshiba 20 TB listing therefore tells you little until you have read the generation in its part number.

20TB SAS drive price on Amazon.co.uk

The first table holds 1 listing right now. Prices are pounds sterling inc VAT. This table follows the interface our catalogue records for each listing, and that record is only as good as its source. An Ultrastar HC555 listing, 0B47749, is catalogued as 20 TB SAS. WD's HC555 sheet gives the WUH722020CLxxyz form, and the sheet does not print 0B47749, so that listing's code cannot be matched to it.

Seagate's sheet lists ST20000NM007H under SAS 12 Gb/s, which is why that drive sits in this table even where a listing's title names no interface: the part number is the safer test. The same test works in reverse: a listing titled HC560 0F38785 is a SATA number on WD's sheet.

In-stock alternatives

None of these is the product this page covers: they are what is in stock on Amazon.co.uk beside it right now. Each row says why it is listed. Check the interface, form factor and part number against your system before buying.

20TB SAS Seagate, Ultrastar or Toshiba: power compared

Between the two Seagate generations, X20 SAS is the more frugal on these figures. It idles 0.7 W below the X24-generation 20 TB, and its maximum write figure is 1.2 W lower. Divided by 20, the idle figures come to 0.290, 0.305 and 0.325 W/TB for the X20, HC560 and X24 generation. WD prints 0.28 W/TB for the HC555 in SAS, and Toshiba's merged cell divides to 0.24 W/TB, which is our sum on a group value.

On construction, WD describes the HC560 as a 20 TB capacity in a nine-disk platform, in a standard 3.5-inch form factor. Its interface limit is 1,200 MB/s on SAS against 600 MB/s on SATA. Those are interface limits rather than what the platters sustain, so do not expect a doubling from choosing SAS.

The X20 sheet states a 5-year limited warranty. That is the maker's sheet, and it does not tell you what a particular seller's listing carries. SAS models also negotiate down: the access speed row reads 12.0, 6.0 and 3.0 Gb/s for SAS, against 6.0 and 3.0 Gb/s for SATA, and only the SAS columns say Yes to T10 DIF.

What a 20TB SAS disk needs from your controller and backpanel

This applies to every SAS drive, and we keep the full version on this page. Seagate's knowledge base gives these points, and none of them depends on the capacity:

• SAS drives cannot be plugged into SATA controllers.
• SATA drives may be plugged into SAS controllers, so the rule only runs one way.
• Connecting a SAS drive to a SATA controller will not work, which makes the controller the first thing to check rather than the last.
• The SAS connector is normally located on a SAS backpanel, and the drive should make firm contact with the host's backpanel connector.
• Each SAS drive can have its own cable to a SAS host adapter, with a maximum length of 4 metres.

We have not found a source that lets us name a specific connector for these drives or describe how a particular backplane behaves, so we name neither. Check your host adapter's or server's own documentation. SAS vs SATA sets out the wider comparison between the two interfaces.

Sector formats on a 20TB SAS drive

Sector choice divides these lines. The X20 and X24-generation SAS tables offer 512, 520 or 528 bytes under 512e, and the X24 sheet gives 4096, 4160 or 4224 under 4Kn. Toshiba's MG11 SAS table also lists 520 and 528 byte host sectors. HC560 SAS and HC555 list only 512e and 4Kn: 4096. If your array or controller expects one of the larger sizes, that narrows the choice before price does.

Reformatting has a cost: Seagate warns that switching from 512e to 4Kn with the FastFormat routine deletes all data on the drive. Do it before the drive joins an array rather than after.