SSDs Move Into Liquid-Cooled Servers as Kioxia Adds CM9 Models: How Capacity and Endurance Differ
- What happened: Kioxia has added direct liquid-cooling E3.S models to the CM9 series and begun shipping samples to a limited number of customers.
- Why it matters: It widens the options for building SSDs into liquid-cooled AI servers while keeping PCIe 5.0.
- What to watch next: Sustained performance and cooling effectiveness in compatible servers, along with the mass-production schedule, will inform adoption decisions.
On October 13, 2026, Kioxia added the CM9-DLC series to its enterprise SSD line, the KIOXIA CM9 series. The new models support direct liquid cooling with a cold plate. They use the E3.S server form factor and can also be used in conventional air-cooled environments. As AI workloads push compute higher and raise cooling demands, the options for building PCIe 5.0-generation SSDs into liquid-cooled servers are growing. Sample shipments to a limited number of customers have begun, and selecting these drives requires looking beyond transfer speed to compatibility with cooling equipment and daily write volume.
CM9 Extends to Liquid-Cooled Servers While Staying on PCIe 5.0
CM9-DLC supports a method in which a cold plate contacts the SSD to carry heat away. Kioxia's announcement explains that direct liquid cooling advances energy savings and can cool more servers per rack than air cooling. However, it does not give figures for the temperature reduction or power savings when using CM9-DLC, so the actual benefit will need to be verified together with the server configuration.
The drives keep the PCIe 5.0 interface and the NVMe 2.0 protocol. In the E3.S form factor they support dual-port operation, as well as NVMe-MI 1.2c and OCP Datacenter NVMe SSD v2.5. Sequential performance reaches up to 14.8 GB/s for reads and up to 11 GB/s for writes, measured with 128 KiB data at a queue depth of 32. Queue depth refers to the number of requests waiting to be processed at the same time.
This bandwidth is not a figure that was first reached through liquid cooling. The product table for the existing CM9-R E3.S also lists up to 14,800 MB/s reads and 11,000 MB/s writes. At the same time, performance values differ by capacity even within the existing models, so the series-wide maximum should not be read as the performance of the highest-capacity model. What is new in this announcement is that cooling options have been added without changing the CM9's interface generation.
This is also not Kioxia's first liquid-cooled SSD. In its July 30 CM10 announcement, the company had indicated liquid-cooling support for a PCIe 6.0 E3.S and a 9.5 mm-thick E1.S. With CM9-DLC, the range of liquid-cooling-capable products now extends beyond the newer-generation products announced earlier to configurations using PCIe 5.0.
Context Caching Use Cases Aren't Decided by Capacity Alone
CM9-DLC comes in two versions: the read-intensive CM9-DLC-R and the CM9-DLC-V for mixed read/write workloads. Both use BiCS FLASH TLC, but they differ in the combination of capacity and write endurance. For context caching, the use case Kioxia cited for this release, which means holding the context data used in AI inference, this difference matters in selection.
In its March 17 announcement, the company also addressed the relationship between the growing KV cache and the CM9. It positioned the 25.6 TB, 3 DWPD CM9 for configurations such as NVIDIA CMX, which extends the memory hierarchy beyond GPU memory with high-performance storage. SSDs are expected not only to store data for long periods but also to absorb the data used in inference. That said, this CM9-DLC announcement does not present adoption in a specific CMX configuration or measured results.
DWPD indicates how many times per day the drive's full capacity can be written so that total rated write volume is reached at the end of its rated lifetime. Even when comparing 1 DWPD and 3 DWPD, the daily data volume differs if the drive capacities differ. Lining up the CM9-DLC configurations from the official product table gives the following.
| Item | CM9-DLC-R | CM9-DLC-V |
|---|---|---|
| Intended use | Read-intensive | Mixed read/write |
| Capacity lineup | 7.68 / 15.36 / 30.72 TB | 6.4 / 12.8 / 25.6 TB |
| Rated endurance | 1 DWPD | 3 DWPD |
| Approx. daily writes, largest model | 30.72 TB/day | 76.8 TB/day |
Based on the nominal capacity and DWPD of the largest models, the approximate daily write volume is 30.72 TB for the CM9-DLC-R and 76.8 TB for the CM9-DLC-V, making the latter 2.5 times the former.
This is calculated from the values in Kioxia's October 13 announcement, using 30.72 × 1 for the R and 25.6 × 3 for the V. The ratio comes from 76.8 ÷ 30.72. It is not a comparison of SSDs with the same capacity, but a write volume averaged over the rated lifetime in days, and it does not mean that transfer speed or actual lifespan is 2.5 times greater. The product table is marked "Preliminary," so the sample specifications may change at mass production.
The R's largest model can store more data, while the V's largest model has the higher approximate daily write volume. The model to choose therefore depends on how much context cache must be held and how often it is updated. Support for liquid cooling alone does not settle the choice between capacity and endurance.
Contact Surfaces and Pressure Underpin Liquid-Cooling Support
Even when the E3.S form factor name matches, an older SSD cannot necessarily be installed as-is in a liquid-cooled server. SNIA's published "SFF-TA-1008" Rev 3.0a defines the cooling surfaces used in liquid cooling and the regions that support them. Reading this July 10, 2026 version of the specification shows why liquid-cooling support is more than simply adding a cold plate to the outside.
Section 5.2 of the specification covers single-sided and double-sided cooling for E3.S and E3.L. When pressure is applied from one side, it shows a configuration with support on the bottom side; when both sides are used, it recommends applying equal and opposite forces. It also provides for handling 103 kPa of pressure on the cooling surface, and states that it is the host's responsibility to ensure that excessive shear force is not applied to the connection terminals or connectors. Releasing heat requires contact, and maintaining that contact requires mechanical design.
Section 5.7 further specifies keying to prevent incorrect insertion. The aim is to prevent older devices not designed for liquid cooling from being inserted into a liquid-cooled system and damaged by pressures they were not designed for. This is a requirement of the E3 specification as a whole and does not mean CM9-DLC has been certified to a particular version of it. Even so, it makes clear why adopters cannot judge compatibility from the form factor name alone.
Kioxia's announcement and product table do not list compatible cold plates or servers, coolant conditions, or sustained performance under liquid cooling. Pricing and the start of mass production are also information to come, and what is currently available are samples for functional evaluation. The company also announced a display at the OCP Global Summit, held October 12–15 in San Jose, California.
When adopting the drives, buyers will need to estimate the cache capacity they must hold and their daily write volume, then measure sustained performance and cooling load once the drives are installed in compatible servers. Once that evaluation is complete, it should provide the basis for deciding whether to build a liquid-cooled configuration that includes the SSDs while keeping a PCIe 5.0 connection.