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Z-NAND is Samsung’s specialized, low-latency NAND flash technology—not a type of DRAM. It uses the same fundamental vertical-NAND (V-NAND) concept as Samsung’s conventional flash, but adds a different circuit design and controller approach. Samsung paired Z-NAND with a controller and LPDDR4 DRAM in its enterprise SZ985 Z-SSD, where the flash provided persistent storage and the DRAM served as volatile working memory.
The important qualification is scope: the best-documented figures are Samsung’s 2017–2018 specifications for the 800GB SZ985 and Samsung’s own comparator products. They show how that product was positioned, not a current, independent benchmark proving that every Z-NAND device is faster, cheaper or better than all NAND and DRAM.
What Z-NAND is
Z-NAND is a Samsung flash-memory technology designed to reduce storage latency while retaining NAND flash’s non-volatile behavior. “Non-volatile” means that data remains stored when power is removed. Samsung described Z-NAND as sharing V-NAND’s fundamental structure while using a distinct circuit design and controller strategy to improve performance. The technology was used in Samsung’s Z-SSD products, with the SZ985 being the clearest documented example.
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Samsung introduced Z-SSD as a low-latency storage option in 2016, presented the SZ985 for data-center and enterprise workloads in 2017, and announced an 800GB SZ985 for high-performance-computing (HPC) and artificial-intelligence applications in 2018. The original positioning emphasized real-time analytics, server caching and other data-intensive work rather than ordinary consumer laptop storage. Samsung’s 2016 announcement is available in its Z-SSD technology overview.
How Z-NAND differs from ordinary NAND
All NAND flash stores information in electrically programmable cells and keeps that information without continuous power. Conventional NAND products optimize a combination of density, cost, endurance and speed. Samsung’s V-NAND stacks cells vertically to increase density; 3-bit-per-cell V-NAND stores three bits in each cell and is commonly used for high-capacity SSDs.
Z-NAND uses a different balance. Samsung’s design reduced the time needed to read cells and paired the flash with a controller intended for very low response times. In its 2018 launch announcement, Samsung reported 10 times higher cell-read performance than its own 3-bit V-NAND chips. That is a chip-level, vendor-reported comparison from a named product generation. It should not be interpreted as “every Z-NAND SSD is ten times faster than every NAND SSD,” because whole-drive performance includes the controller, interface, firmware and host system.
NAND also exists in several generations, cell types and interfaces. A current high-density NAND SSD can have greater capacity or lower cost per gigabyte than an older Z-SSD, while a modern controller and PCIe interface can change application results. The available SZ985 documents do not provide a contemporary, cross-vendor comparison with current consumer or enterprise SSDs.
Z-NAND versus NAND and DRAM at a glance
| Technology or product | What it is | Persistence and system role | Evidence available for this comparison |
|---|---|---|---|
| Conventional NAND / Samsung V-NAND | Flash memory; V-NAND is Samsung’s vertically stacked implementation | Non-volatile storage for SSDs and other devices | Samsung compared Z-NAND cell-read performance with its 3-bit V-NAND chips in 2018. |
| Z-NAND | Samsung flash technology used in Z-SSD products | Non-volatile storage; data remains after power loss | Samsung described a shared V-NAND structure with circuit and controller changes, and reported a 10× cell-read advantage over its 3-bit V-NAND chips in the 2018 launch material. |
| DRAM | Dynamic random-access memory, including LPDDR4 in the SZ985 | Volatile working memory; contents are lost when power is removed | Samsung’s brochure explicitly distinguishes DRAM’s volatility from flash storage. |
| SZ985 Z-SSD | An 800GB enterprise SSD combining Z-NAND, controller, DRAM and PCIe | Persistent storage for data-intensive enterprise workloads | Samsung listed PCIe Gen3 ×4, half-height half-length form factor, 20/16 microsecond typical read/write latency and up to 30 drive writes per day for five years. |
The table compares different layers. NAND and Z-NAND are storage media; DRAM is working memory; the SZ985 is a complete drive. Comparing them as if they were interchangeable products leads to incorrect conclusions about capacity, persistence and performance.
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Is Z-NAND the same as DRAM?
No. Z-NAND is non-volatile flash storage, while DRAM is volatile memory. A system uses DRAM to hold active program data, operating-system pages and caches at very low latency. It must be continually refreshed and normally loses its contents when power stops. NAND stores files and database blocks persistently, but its erase and program operations are slower and occur in larger pages and blocks.
The SZ985 demonstrates the relationship clearly: Samsung included 1.5GB of LPDDR4 DRAM alongside Z-NAND in the 800GB drive. The DRAM did not turn the flash into memory or replace system RAM. It supported the drive’s controller and mapping operations, while Z-NAND supplied the persistent capacity. Samsung’s 2018 launch announcement describes this component combination in the SZ985 product announcement; the technical brochure provides the detailed specifications at Samsung’s SZ985 specification PDF.
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Samsung published several figures for the 800GB SZ985. They describe a 2018 enterprise product and are manufacturer specifications, not independent tests performed for this article.
| Metric | Samsung-published figure | How to interpret it |
|---|---|---|
| Random-read IOPS | 750,000 | Launch specification for the 800GB SZ985; actual results depend on queue depth, block size, software and hardware. |
| Random-write IOPS | 170,000 | Launch specification for the same product and test context; not a universal Z-NAND value. |
| Typical read/write latency | 20/16 microseconds | Values listed in Samsung’s April 2018 brochure; “typical” is not a guaranteed response for every request. |
| Write latency | 16 microseconds | Also stated in Samsung’s 2018 launch material; it is a drive-level specification. |
| Read latency | 15 microseconds | Figure used in Samsung’s 2017 announcement, where it was described as about one-seventh of an NVMe SSD; it comes from a different document and context than the 20-microsecond brochure figure. |
| Endurance | Up to 30 drive writes per day for five years | Samsung’s endurance claim for the SZ985, equivalent to rewriting the drive’s rated capacity up to 30 times per day over that period under the stated qualification. |
Samsung also compared the SZ985 with its PM963 NVMe SSD in product-era announcements. That comparison is not interchangeable with the 10× cell-read statement: one concerns drive-level behavior against a named SSD, while the other concerns cell-read performance against Samsung’s 3-bit V-NAND chips. Neither figure establishes application-level acceleration for every database, virtual machine or AI workload.
Latency and IOPS should be read together with workload conditions. Random reads at a particular queue depth can look excellent while sustained writes, mixed workloads, thermal limits or synchronization-heavy applications produce different results. A storage administrator should request test data using the application’s block size, read/write ratio, queue depth and durability settings before treating a vendor number as a capacity-planning assumption.
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Why Z-NAND was designed
Flash SSDs are much faster than hard disks, but enterprise applications can still spend significant time waiting on storage. Real-time analytics, server-side caching, high-performance databases and AI pipelines often issue many small random requests. Lower tail latency can matter more than peak sequential bandwidth because a few slow requests can delay dependent work.
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Samsung positioned the SZ985 for data centers, HPC systems and AI-related workloads. Its launch statement described the drive as intended for “today’s artificial intelligence (AI), big data and Internet of Things (IoT) applications,” emphasizing high performance, reliability and ultra-low latency. That is a company positioning statement, not independent evidence that every application will improve by a fixed percentage.
Z-NAND’s trade-off was therefore specialization. The design prioritized response time and endurance over the maximum density and lowest possible cost per gigabyte that characterize many mainstream NAND products. An enterprise buyer might accept a smaller, older-generation drive if predictable latency and write endurance reduce server bottlenecks; a consumer storing media files usually benefits more from capacity and price.
Capacity, endurance and cost context
The documented SZ985 capacity was 800GB. Samsung specified the drive as PCIe Gen3 ×4 and half-height, half-length (HHHL), a form factor commonly used with enterprise add-in cards. Those details affect whether a server has the required slot, lane allocation, airflow and firmware support.
There is no reliable contemporary price or availability figure established for the SZ985 in the supplied product documents. The announcements and brochure date from 2017–2018, so listings found today may be used, refurbished or counterfeit. A 30-drive-writes-per-day rating also does not guarantee that a used drive has any remaining endurance; remaining-life data must be checked through the controller’s health information.
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Cost comparisons should include the whole platform. DRAM is priced and expanded as volatile memory, while NAND is purchased as persistent capacity. A low-latency SSD may reduce the amount of DRAM needed for a cache, but it cannot provide DRAM’s refresh behavior or memory-bus bandwidth. Conversely, adding RAM does not create durable storage for files or databases.
Workloads that could benefit—and those that may not
Potentially suitable workloads
- High-concurrency random reads: analytics and transactional systems that issue many small reads can be sensitive to storage response time.
- Server caching: a persistent, high-endurance device can absorb frequent cache updates without relying entirely on volatile memory.
- AI and HPC scratch data: preprocessing and checkpoint workflows may benefit from lower storage latency when the software is I/O-bound.
- Write-intensive enterprise services: the published 30-DWPD, five-year rating was aimed at substantially heavier writing than a typical desktop workload.
Workloads unlikely to justify a specialized legacy drive
- Large sequential media files: capacity, sustained bandwidth and price per terabyte usually matter more than microsecond random-access latency.
- Memory-bound applications: if the working set fits in system DRAM, replacing a storage device may not change execution time.
- Light desktop use: web browsing, office documents and occasional game loading rarely exploit enterprise endurance ratings.
- Systems without PCIe Gen3 ×4 HHHL support: physical and electrical incompatibility can prevent installation regardless of the drive’s specifications.
Checking whether an SZ985 would fit a server
The following checks are necessary before treating the SZ985 as an upgrade. They are compatibility checks, not a recommendation to purchase an old product.
- Confirm the exact model. Verify that the label and firmware identify an SZ985 Z-SSD, not a similarly named Samsung SSD using conventional NAND.
- Check the interface. The documented drive uses PCIe Gen3 ×4. Confirm that the host provides four PCIe lanes at the required generation and supports the drive’s NVMe behavior.
- Check the form factor and slot. Samsung lists a half-height, half-length add-in-card form factor. Verify bracket height, slot clearance, lane bifurcation and airflow.
- Review platform support. Check server-vendor qualification lists, BIOS settings, operating-system NVMe drivers and firmware-update procedures. An electrically compatible card can still be unsupported.
- Measure the workload. Record read/write ratio, block size, queue depth, synchronization frequency, latency percentiles and daily writes before and after a controlled test.
- Inspect health data on used hardware. Read total bytes written, percentage used, media errors and spare-capacity indicators. A historical endurance rating does not reveal the remaining life of a second-hand unit.
- Plan replacement and backup. High endurance is not immunity from controller failure, NAND wear, firmware defects or host faults. Keep normal backups and a rollback device.
Common misconceptions about Z-NAND
“Z-NAND is a new kind of RAM.”
It is not. Z-NAND remains flash storage and retains data without power. DRAM remains the volatile working-memory layer, including the LPDDR4 used inside the SZ985.
“Ten times faster” applies to the whole computer.
Samsung’s 10× statement referred to cell-read performance versus its 3-bit V-NAND chips in a 2018 comparison. It does not predict a tenfold reduction in database response time, application runtime or whole-system throughput.
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They come from different Samsung documents. The 2017 announcement used a 15-microsecond read-latency figure; the April 2018 brochure listed typical read/write latency of 20/16 microseconds. Keep the source, date and metric attached to each number rather than combining them into one universal specification.
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“Z-NAND is always better than newer NAND.”
That conclusion is unsupported. The documented device is from the 2018 product era. Newer NAND generations, controllers and PCIe interfaces may offer more capacity, bandwidth or better economics. Only a workload-specific, current comparison can establish which option is preferable.
“zNAND-O is the same product as the SZ985.”
Samsung used a similar name for a different 2026 roadmap concept. In August 2026, it described zNAND-O as a V-NAND-based, high-performance NAND solution under development for edge-AI applications, with four- and eight-layer concept models. The announcement does not establish that zNAND-O is the SZ985-era implementation or a shipping replacement. Read the separate 2026 Samsung announcement in its own context.
What is known—and what is not
The documented facts support a clear description: Z-NAND is Samsung non-volatile flash technology associated with low-latency Z-SSD products; the SZ985 combined it with a controller and LPDDR4 DRAM; Samsung reported high random I/O, microsecond-scale latency and a 30-DWPD endurance rating for that 800GB enterprise drive.
They do not establish a current market-wide ranking, an independent benchmark against modern NAND SSDs, a current street price, or guaranteed availability. They also do not show that Z-NAND can replace DRAM. Any purchasing or architecture decision should therefore separate three questions: whether the workload needs persistent storage, whether its bottleneck is storage latency, and whether a currently supported device meets the host’s interface, endurance and service requirements.
Bottom line for system designers
Z-NAND occupies a middle ground between ordinary high-density NAND and volatile DRAM: it targets much lower flash-storage latency while preserving data without power. The SZ985 illustrates the design philosophy, combining specialized flash with a controller and a small DRAM component rather than trying to make flash behave like system RAM. Its Samsung-published 2017–2018 numbers remain useful for understanding the product’s intent, but they should be treated as historical, vendor-attributed specifications. For a real deployment, compare a supported current drive and the existing DRAM configuration using the application’s measured latency, endurance and cost requirements.
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