Enterprise HDD Model Families: Seagate Exos, WD Ultrastar, Toshiba MG Explained
Three manufacturers — Seagate, Western Digital, and Toshiba — make nearly all enterprise hard drives. Each uses its own family naming, but the families are rough competitive equivalents: same capacity tier and release year means the same target workload. Once you know the families, you can find the cross-brand equivalent and understand what generation a drive belongs to.
The three makers at a glance
Seagate’s enterprise flagship is the Exos line. The X-series (X16, X18, X20, X22, X24) uses the number to signal areal density generation — higher number means newer platters and a higher capacity ceiling. Mozaic is Seagate’s HAMR (heat-assisted magnetic recording) platform, debuting at 28TB+ and representing the post-CMR generation of drives.
Western Digital’s enterprise line is Ultrastar DC, with model numbers using an HC prefix (HC330, HC530, HC550, HC560, HC570, HC580). Higher number = newer generation with a higher capacity ceiling. The HC5xx series covers the current high-capacity tier (16–24TB).
Toshiba uses the MG prefix followed by a two-digit generation number (MG07, MG08, MG09, MG10, MG11). It’s the most straightforward of the three — the number increments each generation. Current active procurement focuses on MG09 through MG11.
SeagateExos family decoder
| Family | Year | Capacity range | Recording tech | Notes |
|---|---|---|---|---|
| X16 | 2019 | 12–16 TB | CMR | 7,200 RPM, 256 MB cache; 6-platter design |
| X18 | 2020 | 12–18 TB | CMR | 7,200 RPM, 256 MB cache; improved areal density over X16 |
| X20 | 2022 | 18–20 TB | CMR | 7,200 RPM, 256 MB cache; 9-platter |
| X22 | 2023 | 20–22 TB | CMR | 7,200 RPM, 512 MB cache; highest CMR density at launch |
| X24 | 2024 | 20–24 TB | CMR | 7,200 RPM, 512 MB cache; current flagship CMR |
| Mozaic 3+ | 2024–25 | 28–32 TB+ | HAMR | Next-gen platform; different thermal requirements — not a drop-in for CMR slots |
All Exos X-series available in SATA 6Gb/s and SAS 12Gb/s variants. Mozaic currently SAS-only in most enterprise configs.
WDUltrastar DC family decoder
| Family | Year | Capacity | Recording tech | Notes |
|---|---|---|---|---|
| HC330 | 2019 | 10 TB | CMR | 7,200 RPM, 256 MB cache; entry high-cap tier |
| HC530 | 2019 | 14 TB | CMR | 7,200 RPM, 512 MB cache |
| HC550 | 2020 | 16–18 TB | CMR | 7,200 RPM, 512 MB cache; helium-sealed |
| HC560 | 2021 | 20 TB | CMR | 7,200 RPM, 512 MB cache; 9-platter helium |
| HC570 | 2022 | 22 TB | CMR | 7,200 RPM, 512 MB cache |
| HC580 | 2023–24 | 24 TB | CMR / UltraSMR | Current flagship; UltraSMR variant available for cold-storage workloads |
HC prefix = Helium Capacity. All HC5xx series are helium-sealed. SATA and SAS variants share the same HC model number — check the full part number suffix for interface.
ToshibaMG series decoder
| Family | Year | Capacity range | Recording tech | Notes |
|---|---|---|---|---|
| MG07 | 2018–19 | 12–14 TB | CMR | 7,200 RPM, 256 MB cache |
| MG08 | 2019–20 | 14–16 TB | CMR | 7,200 RPM, 256 MB cache; helium |
| MG09 | 2021 | 14–18 TB | CMR | 7,200 RPM, 512 MB cache; 9-platter |
| MG10 | 2023 | 16–20 TB | CMR | 7,200 RPM, 512 MB cache |
| MG11 | 2024 | 20–24 TB | CMR | Current generation; 512 MB cache |
Toshiba appends interface and capacity to the model number (e.g. MG09ACA18TE = MG09, SATA, 18TB). See part number decoder below.
Cross-brand equivalents
Drives in the same capacity tier from the same release window compete for the same workloads. These pairings are directional — workload rating, cache, power draw, and firmware differ across brands even at the same capacity.
| Capacity | Interface | Seagate | WD Ultrastar | Toshiba |
|---|---|---|---|---|
| 10 TB | SATA / SAS | Exos X10 | HC330 | MG06 |
| 14 TB | SATA / SAS | Exos X16 (14TB) | HC530 | MG07 / MG08 |
| 16 TB | SATA / SAS | Exos X18 (16TB) | HC550 (16TB) | MG08 |
| 18 TB | SATA / SAS | Exos X18 (18TB) | HC550 (18TB) | MG09 |
| 20 TB | SATA / SAS | Exos X20 | HC560 | MG10 (20TB) |
| 22 TB | SATA / SAS | Exos X22 | HC570 | — |
| 24 TB | SATA / SAS | Exos X24 | HC580 (24TB) | MG11 (24TB) |
— = no direct equivalent at this capacity from that manufacturer at time of writing.
How to read an HDD part number
SeagateST18000NM000J
| Segment | Value | Meaning |
|---|---|---|
| Brand | ST | Seagate |
| Capacity | 18000 | 18,000 GB = 18 TB |
| Market | NM | NearLine / Enterprise (NM = high-cap NAS/enterprise) |
| Interface | 000 | SATA 6Gb/s (001 = SAS 12Gb/s) |
| Variant | J | Minor hardware revision / firmware generation |
WDWUH721818ALE6L4
| Segment | Value | Meaning |
|---|---|---|
| Platform | WUH | Ultrastar He (WD Ultrastar helium) |
| Generation | 72 | 7th-gen, 2-platter-per-head tier (internal platform code) |
| Capacity | 18 | 18 TB |
| Interface | A | SATA (C = SAS) |
| Form factor | LE | 3.5-inch enterprise |
| Revision | 6L4 | Firmware / hardware variant code |
ToshibaMG09ACA18TE
| Segment | Value | Meaning |
|---|---|---|
| Family | MG09 | MG generation 9 |
| Interface | A | SATA (B = SAS) |
| Form factor | C | 3.5-inch (standard enterprise) |
| Capacity | 18 | 18 TB |
| Revision | T | 512-byte sector emulation (E suffix) |
| Region | E | For international markets (other codes = regional variants) |
SATA vs SAS
SATA (6Gb/s) covers the majority of enterprise capacity-tier workloads — backup, archive, bulk object storage, and most NAS deployments. SAS (12Gb/s) is used where dual-port / multipath access is required: shared storage arrays, SAN environments, and tier-1 systems that need the drive to stay accessible if one controller path fails. SAS drives typically carry a 15–30% price premium over equivalent SATA models at the same capacity, reflecting the lower volume and dual-port hardware cost.
OEM variants
Dell, HPE, Lenovo, and Supermicro sell rebranded versions of all three manufacturers’ drives under their own part numbers — an HPE 656108-001 is effectively a Seagate or WD drive with HPE firmware and an HPE label. These OEM variants often carry a significant premium over equivalent manufacturer-direct drives, driven by vendor support contracts, firmware qualification, and captive buyer behavior. The underlying drive is usually identifiable from the model string or a label under the OEM sticker. OEM vs Tray certification explained →
How this connects to pricing
Drives of the same capacity tier across brands trade in a relatively tight band on the secondary market — buyers have cross-brand options, which keeps pricing competitive. OEM variants (HPE, Dell, Lenovo labels) trade at a structural premium above this band, regardless of the underlying drive. If you see a large price gap between two 18TB drives, check whether one is OEM-labeled before concluding there’s a quality difference.
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