# Fanxiang S660 4TB Review — Four Terabytes of QLC on a Budget (2026)

The Fanxiang S660 4 TB is the biggest, cheapest PCIe 4.0 drive you can buy — and it is unapologetically QLC, which means you trade write stamina for capacity and hope the price makes up for it.

Quick answer: The Fanxiang S660 4 TB is for the buyer who wants the most gigabytes per dollar in a PCIe 4.0 form factor and is willing to treat the drive as disposable — a Steam library repository, a Plex media drive, or a local backup target where every byte exists elsewhere. It is not a primary boot drive, not a workstation scratch disk, and certainly not the place to store the only copy of anything. If that describes your use case, the S660 4 TB delivers unbeatable capacity economics. If it does not, the Crucial P3 Plus 4 TB costs more but comes from a company that still answers the phone.

## Specifications

| Specification | Value |
| --- | --- |
| Capacity | 4 TB |
| Interface | M.2 4.0 x 4 |
| Controller | Phison PS5021-E21T 4 Channel |
| Memory type | Micron 176-L QLC |
| DRAM cache | No |
| Sequential read | 5000 MB/s |
| Sequential write | 4500 MB/s |
| Random read IOPS | 600000 |
| Random write IOPS | 500000 |
| Endurance | 2800 TBW |
| MTBF | 1500000 |
| Warranty | 5 years |

## Performance

The S660 4 TB is rated for 5,000 MB/s sequential reads and 4,500 MB/s sequential writes, with random IOPS around 600,000 reads and 500,000 writes. The large capacity provides ample NAND dies to saturate these ratings, and the pseudo-SLC cache pool is generous enough that most consumer workloads — even large game installs — complete before the cache fills.

When the cache does exhaust, writes degrade through a folding phase at roughly 1,400 MB/s before settling to native QLC speed around 530 MB/s. This is the same behaviour as every other QLC drive in this class; the S660's advantage at 4 TB is simply that the cache is larger, so you hit the cliff less often. For a bulk media library, game repository, or backup target where writes are large but infrequent, this performance profile is acceptable. For a primary workstation drive or any role involving daily large data ingest, QLC remains the wrong tool regardless of capacity.

## Endurance, TBW & Warranty

The 4 TB S660 carries a confirmed 2,800 TBW endurance rating and a claimed 5-year warranty. At 50 GB per day, the endurance budget stretches to over 150 years — QLC endurance concerns at this capacity are mathematically irrelevant for consumer workloads. The MTBF is rated at 1.5 million hours, with the standard caveat that this is a population statistic. The real warranty limitation is Fanxiang's support responsiveness: the S660 does not appear on the company's website, RMA requests reportedly go unanswered, and some users have only obtained refunds through retailer intervention. A 5-year warranty from an unreachable company is worth less than a 3-year warranty from a responsive one.

## Pros and Cons

**Pros:**

- 4 TB of PCIe 4.0 storage at the lowest price in its class
- Confirmed 2,800 TBW endurance — ample for any consumer workload
- Single-sided PCB with included heatsink fits laptops and PS5
- Large SLC cache buffer minimises real-world QLC write cliff encounters
- Includes mounting hardware and screwdriver in the box
**Cons:**

- QLC NAND write cliff drops sustained writes to ~530 MB/s once cache fills
- DRAM-less HMB design limits mixed-workload consistency
- Marketed as TLC on some retailer listings but objectively QLC per Flash ID analysis
- Warranty support practically non-existent — RMA requests go unanswered
- At 4 TB, a drive failure represents a significant data loss if not backed up


## Verdict

The Fanxiang S660 4 TB is for the buyer who wants the most gigabytes per dollar in a PCIe 4.0 form factor and is willing to treat the drive as disposable — a Steam library repository, a Plex media drive, or a local backup target where every byte exists elsewhere. It is not a primary boot drive, not a workstation scratch disk, and certainly not the place to store the only copy of anything. If that describes your use case, the S660 4 TB delivers unbeatable capacity economics. If it does not, the Crucial P3 Plus 4 TB costs more but comes from a company that still answers the phone.

## Frequently Asked Questions

### Is the Fanxiang S660 4TB TLC or QLC?

It is QLC. ServeTheHome confirmed Micron 176-layer QLC (N48R) via Flash ID analysis of the 4 TB model. Some Amazon and retailer listings incorrectly label the drive as TLC — this is either a listing error or deliberate misrepresentation. If you need TLC at this capacity and price point, you will need to look at a different drive or accept a higher price.

### What is the TBW endurance of the Fanxiang S660 4TB?

2,800 TBW, as confirmed by ServeTheHome's review. This is a strong endurance rating for a QLC drive and reflects the capacity advantage — more NAND to spread writes across. At a heavy consumer workload of 50 GB per day, 2,800 TBW provides over 150 years of write endurance, making the TBW ceiling effectively unreachable under normal use.

### Is the Fanxiang S660 4TB good for a game library?

This is arguably the S660 4 TB's ideal use case. A game library is write-once-read-many: you download a game once, then read it thousands of times. The 5,000 MB/s reads handle DirectStorage and texture streaming without issue, the QLC write cliff is irrelevant after initial installation, and the 4 TB capacity holds a large collection. With cloud saves enabled on your platform, a drive failure costs you only the time to re-download.

### Is the Fanxiang S660 4TB compatible with the PS5?

The single-sided M.2 2280 form factor with the included heatsink fits the PS5 expansion bay well. However, the S660's 5,000 MB/s read rating is below Sony's 5,500 MB/s recommendation. The PS5 will still format the drive and games will run, but some titles may exhibit slightly longer load times or occasional streaming hitches compared to a drive meeting the full recommendation.

### How does the Fanxiang S660 4TB compare to the Crucial P3 Plus 4TB?

Architecturally, they are nearly identical — same Phison E21T controller, same Micron QLC NAND supply chain, same HMB-based DRAM-less design. The Crucial benefits from Micron's direct brand ownership (firmware, validation, support) and a functional global warranty process. The S660 undercuts it on price. If you are buying for bulk storage where data is replaceable, the Fanxiang's price advantage is compelling. If this is your only drive or holds irreplaceable data, the Crucial's support infrastructure justifies the premium.

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Last updated: 2026-08-10. Source: https://ssdrive.net/fanxiang-s660-4-tb