NAS Drive Compatibility

Western Digital Ultrastar DC HC550 18TB

Enterprise HDD

Part number WUH721818ALE6L1 · Ultrastar DC HC550 series · SATA 6Gb/s (SATA III). If your machine is listed below, this drive is officially supported — not a forum workaround.

Ultrastar DCHC550NAS HARD DRIVE3.5" SATA HDDWESTERN DIGITAL

Part of the Western Digital Ultrastar DC HC550 series →

Check WUH721818ALE6L1 price on Amazon  partner link

95
Compatible NAS models
0 Syn · 94 QNAP · 1 Asus · 0 TM
By vendor
18 TB
Listed capacity
Western Digital
Manufacturer
Enterprise capacity
Product line (manufacturer rating)
7200
Spindle speed (RPM)
CMR
Recording
512 MB
Cache
550 TB
Rated workload / year

Specifications are the manufacturer's published ratings for this product series; verify the exact part number before purchase.

Strong pick as a cold copy

Rated CMR (conventional magnetic recording) — the right recording type for a large cold copy. CMR keeps a full-library backup pass fast even at 16–24 TB, which is the whole point of the offline slot in a 3-2-1 plan: rotate two drives monthly, keep one powered off, and the backup tooling (Veeam, Duplicati, Hyper Backup, HBS 3) does the scheduling. Full rule and vendor tool table: 3-2-1 for NAS.

Compatibility verdict

It appears on the official compatibility lists of 95 machines and series — 94 QNAP, 1 Asustor. This is a Enterprise-class drive: rated for heavier sustained workloads than desktop drives. It is a strong pick for a NAS running 24/7, large-array rebuilds or camera workloads, and enterprise lines are also the drives most widely listed across all five vendors' HCLs. Its series rating is on file as CMR (conventional) — what RAID rebuilds and full-library copies want.

Compatible NAS models

QNAP TL-D1600S See its full HCL → QNAP TL-D400S See its full HCL → QNAP TL-D800C See its full HCL → QNAP TL-D800S See its full HCL → QNAP TL-R1200C-RP See its full HCL → QNAP TL-R1200PES-RP See its full HCL → QNAP TL-R1200S-RP See its full HCL → QNAP TL-R1600PES-RP See its full HCL → QNAP TL-R400S See its full HCL → QNAP TR-002 See its full HCL → QNAP TS-1232PXU-RP See its full HCL → QNAP TS-1264U-RP See its full HCL → QNAP TS-1273AU-RP See its full HCL → QNAP TS-1277XU-RP See its full HCL → QNAP TS-1283XU-RP See its full HCL → QNAP TS-133 See its full HCL → QNAP TS-1635AX See its full HCL → QNAP TS-1655 See its full HCL → QNAP TS-1673AU-RP See its full HCL → QNAP TS-1677XU-RP See its full HCL → QNAP TS-1683XU-RP See its full HCL → QNAP TS-216G See its full HCL → QNAP TS-233 See its full HCL → QNAP TS-2477XU-RP See its full HCL → QNAP TS-251D See its full HCL → QNAP TS-253B See its full HCL → QNAP TS-253E See its full HCL → QNAP TS-262 See its full HCL → QNAP TS-264 See its full HCL → QNAP TS-433 See its full HCL → QNAP TS-435XeU See its full HCL → QNAP TS-453D See its full HCL → QNAP TS-453E See its full HCL → QNAP TS-462 See its full HCL → QNAP TS-464 See its full HCL → QNAP TS-464U See its full HCL → QNAP TS-464U-RP See its full HCL → QNAP TS-464eU See its full HCL → QNAP TS-467X See its full HCL → QNAP TS-473A See its full HCL → QNAP TS-664 See its full HCL → QNAP TS-667X See its full HCL → QNAP TS-673A See its full HCL → QNAP TS-855X See its full HCL → QNAP TS-855eU See its full HCL → QNAP TS-855eU-RP See its full HCL → QNAP TS-864eU See its full HCL → QNAP TS-864eU-RP See its full HCL → QNAP TS-867X See its full HCL → QNAP TS-873A See its full HCL → QNAP TS-873AeU See its full HCL → QNAP TS-873AeU-RP See its full HCL → QNAP TS-877XU See its full HCL → QNAP TS-877XU-RP See its full HCL → QNAP TS-883XU See its full HCL → QNAP TS-883XU-RP See its full HCL → QNAP TS-977XU See its full HCL → QNAP TS-977XU-RP See its full HCL → QNAP TS-983XU See its full HCL → QNAP TS-983XU-RP See its full HCL → QNAP TS-h1065eU See its full HCL → QNAP TS-h1065eU-RP See its full HCL → QNAP TS-h1277AXU-RP See its full HCL → QNAP TS-h1277XU-RP See its full HCL → QNAP TS-h1655XeU-RP See its full HCL → QNAP TS-h1677AXU-RP See its full HCL → QNAP TS-h1677XU-RP See its full HCL → QNAP TS-h1886XU-RP R2 See its full HCL → QNAP TS-h1887XU-RP See its full HCL → QNAP TS-h2287XU-RP See its full HCL → QNAP TS-h2477XU-RP See its full HCL → QNAP TS-h3087XU-RP See its full HCL → QNAP TS-h686 See its full HCL → QNAP TS-h886 See its full HCL → QNAP TS-h966TX See its full HCL → QNAP TS-h973AX See its full HCL → QNAP TS-h977XU-RP See its full HCL → QNAP TS-h987XU-RP See its full HCL → QNAP TVS-472XT See its full HCL → QNAP TVS-672X See its full HCL → QNAP TVS-672XT See its full HCL → QNAP TVS-872X See its full HCL → QNAP TVS-872XT See its full HCL → QNAP TVS-h1277AX See its full HCL → QNAP TVS-h1288X See its full HCL → QNAP TVS-h1677AX See its full HCL → QNAP TVS-h1688X See its full HCL → QNAP TVS-h474 See its full HCL → QNAP TVS-h674 See its full HCL → QNAP TVS-h674T See its full HCL → QNAP TVS-h874 See its full HCL → QNAP TVS-h874T See its full HCL → QNAP TVS-h874X See its full HCL → QNAP TVS-h877AX See its full HCL → Asustor AX7012R See its full HCL →

Same-capacity alternatives

Other drives listed at 18 TB capacity, ranked by how many machines list them:

Seagate ST18000NM000J 211 machines · EXOS x18 Seagate ST18000NE000-2YY101 194 machines · IronWolf Pro Seagate ST18000NT001-3LU101 192 machines · IronWolf Pro Western Digital WUH721818ALE6L4 165 machines · Ultrastar DC HC550 Western Digital WUH721818ALE6L0 162 machines · Ultrastar DC HC550 Western Digital WD181KRYZ 160 machines · Gold Western Digital WD181VRYZ 148 machines · Gold Toshiba MG11ACA18TE 145 machines · MG11 Series

Quick answers

Is the WUH721818ALE6L1 officially compatible with my NAS?

It appears on the official compatibility lists of 95 machines and series — 94 QNAP, 1 Asustor. Every machine page linked below shows the vendor's own list entry, refreshed daily.

Is the WUH721818ALE6L1 CMR or SMR?

As a Western Digital Ultrastar DC HC550 drive, it is rated CMR. CMR (conventional magnetic recording) is what a RAID array wants: SMR drives slow rebuilds dramatically. See the <a href="/faq/cmr-vs-smr-nas-drives/">CMR vs SMR guide</a> for the full series table.

Is the WUH721818ALE6L1 a good NAS drive?

This is a Enterprise-class drive: rated for heavier sustained workloads than desktop drives. It is a strong pick for a NAS running 24/7, large-array rebuilds or camera workloads, and enterprise lines are also the drives most widely listed across all five vendors' HCLs. Its series rating is on file as CMR (conventional) — what RAID rebuilds and full-library copies want.

Can I use the WUH721818ALE6L1 for a 3-2-1 cold backup copy?

Rated CMR (conventional magnetic recording) — the right recording type for a large cold copy. CMR keeps a full-library backup pass fast even at 16–24 TB, which is the whole point of the offline slot in a 3-2-1 plan: rotate two drives monthly, keep one powered off, and the backup tooling (Veeam, Duplicati, Hyper Backup, HBS 3) does the scheduling. Full rule and vendor tool table: 3-2-1 for NAS.

What are alternatives to the WUH721818ALE6L1?

At the same capacity, the most widely listed alternatives are Seagate ST18000NM000J (211 machines), Seagate ST18000NE000-2YY101 (194 machines), Seagate ST18000NT001-3LU101 (192 machines). The full ranked list is below.