Editorial, 22 Aug 2026. Specs from maker pages and named street reports. We have not burned these units in. Affiliate tags are not live. Confirm the diskless SKU before you click — Amazon is full of drive bundles.
2.5-inch vs 3.5-inch in a first NAS: HDD bulk vs SATA SSD apps
Same SATA bay. Do not fill it with an old laptop HDD. 3.5" CMR for bulk. 2.5" SATA SSD when you need IOPS.
Every chassis in this lane takes 3.5" SATA or 2.5" SATA in the same trays: DS224+, DS423+, DXP2800, F2-425, F4-425, AS5402T, AS5404T, F4-424 Pro. That is a tray fact, not permission to recycle a 1 TB 5400 laptop disk with desktop firmware and no RV sensor.
| What | Use | Do not |
|---|---|---|
| 3.5" CMR NAS HDD | Bulk: backups, Photos, media. Example: ST8000VN004 (7200, CMR) or WD80EFPX (5640, CMR). | SMR leftovers. Laptop 2.5" HDD “just to fill a bay.” |
| 2.5" SATA SSD | DSM / UGOS / ADM apps, a small VM volume, a quiet low-power pool. | Assume a client SSD is a NAS-endurance SKU. |
| M.2 NVMe (where the chassis has it) | Cache or a separate SSD pool on DS423+, DXP2800, AS54, F4-424 Pro. | Expect M.2 on F2-425 / F4-425 / DS224+. They do not have it. |
CMR vs SMR still applies the moment the 3.5" disk is in RAID or ZFS. Buy Red Plus / IronWolf / N300. Skip WD Red EFAX, Blue EZAZ, BarraCuda 3.5" 4 / 8 TB SMR. IronWolf 1–6 TB is 5400 RPM; 8 TB ST8000VN004 is 7200. Full table: 2026 CMR picks.
Samsung 870 EVO 2 TB MZ-77E2T0B/AM is compatibility-listed on Asustor AS54 and marketed as NAS-tested. It is still a client SSD (Samsung’s own 2 TB page: 560 / 530 MB/s, 1200 TBW). Prefer Newegg N82E16820147794 or the Samsung US store. Official Samsung US price on that page was $879.99 at the 22 Aug 2026 research fetch. Street moves; do not invent a sale. Amazon B09X198TN5 has a dirty brand field — skip it unless the live card is clearly Samsung. Synology’s own 2.5" line is SAT5200 / SAT5210 (compatibility-list, often pricier).
Skip
Skip used laptop HDDs in a NAS tray. Skip SMR desktop 3.5" in RAID. Skip buying a 2.5" HDD “because it is quieter” when a SATA SSD is the actual IOPS fix and a 3.5" CMR NAS drive is the actual bulk fix. Skip treating 870 EVO TBW as enterprise.
Sources
Darwin’s Data, 2.5 vs 3.5. Orange Hardwares NAS note. Asustor compatibility (870 EVO on AS54). Samsung 870 EVO US spec page. HDD ASINs on the CMR guide. We have not burned these drives in.