Is a PCIe Gen5 NVMe SSD Worth It Over Gen4 for General Servers?

Most buyers asking whether a Gen5 SSD is worth it are not building an AI training cluster. They are refreshing a virtualization host, a database server or a file server, and they see a Gen5 drive quoted next to a Gen4 one with twice the headline read speed. The short answer: Gen5 is worth it when the server is PCIe 5.0 end to end and the workload moves large amounts of data. For many general-purpose servers, a good Gen4 drive is still the right purchase. If you are sizing storage for GPU training instead, our article on Gen5 NVMe for AI storage covers that case.

What does Gen5 actually change compared with Gen4?

PCIe 5.0 doubles the signaling rate per lane over PCIe 4.0, from 16 GT/s to 32 GT/s. An x4 NVMe drive therefore has roughly 16 GB/s of theoretical link bandwidth on Gen5 against roughly 8 GB/s on Gen4. The drives reflect that. The Samsung PM1743 1.92TB is rated up to 14,000 MB/s sequential read and up to 6,750 MB/s sequential write. The Gen4 Samsung PM9A3 960GB is rated up to 6,800 MB/s read and up to 4,200 MB/s write, the same rated figures as the Samsung PM1733 and Micron 7450 PRO.

What Gen5 changes far less is latency on small random I/O at low queue depth, which is what many transactional databases, directory services and VM boot storms actually generate. The link is faster, but the NAND underneath is still NAND. Bandwidth-bound workloads see the doubling. Latency-bound workloads see a much smaller difference.

Do I need a Gen5 server to use a Gen5 SSD?

No, but you need one to get Gen5 speed. PCIe is backward compatible, so a Gen5 drive in a Gen4 server links at Gen4 and performs roughly like a Gen4 drive. For the drive to run at full speed, three things must be Gen5:

• The CPU platform. PCIe 5.0 arrived with 4th Gen Intel Xeon Scalable and AMD EPYC 9004 series processors, which is why servers such as Dell PowerEdge 16th generation and HPE ProLiant Gen11 support it. 3rd Gen Xeon Scalable and EPYC 7003 platforms are Gen4.
• The drive backplane and cabling. A Gen5 server can still be configured with drive bays that are only rated for Gen4. Check the backplane option on the exact chassis configuration, not the platform datasheet.
• The bay type. The PM1743 and Kioxia CM7 drives listed here are U.3, while the PM9A3 is U.2. U.3 drives are designed to work in U.2 NVMe bays, but confirm the bay type and the server vendor's supported-drive list before ordering.

When is Gen5 worth paying for in a general-purpose server?

• Analytics and data warehouse nodes that scan large tables sequentially.
• Dense virtualization hosts where many VMs share a few local drives and aggregate throughput, not single-VM latency, is the limit.
• Software-defined storage nodes that must feed 100GbE or faster networking. One 100GbE port carries about 12.5 GB/s, so fewer Gen5 drives can fill it than Gen4 drives, which frees bays in 1U chassis.
• Scratch and staging tiers for backup, media or build systems that read and write large files.
• New Gen5 servers where the quoted difference is small and the drives will serve the server's full life.

When is a Gen4 NVMe SSD the better buy?

Look at the network before the drive. A 25GbE link moves at most about 3 GB/s, and a single Gen4 drive like the PM9A3 already reads faster than that. If the data leaves the server over 25GbE, Gen5 drives spend most of their time waiting for the network. The same applies wherever storage is not the bottleneck at all: domain controllers, file and print, application servers and most general VM hosts. The full Gen4 range is on our PCIe 4.0 x4 SSD page.

• The server is a Gen4 platform you plan to keep. Buying Gen5 drives now for a future server is rarely good value, because drives are usually refreshed with the server.
• The workload is small-block random I/O at modest queue depth.
• The drive is for boot, logs or a hypervisor install, where a small read-intensive drive is plenty.
• Power and cooling are tight. Gen5 drives generally draw more power and run hotter than Gen4 drives, and dense 1U chassis need the airflow to match.
• You need a capacity point that is easier to source in Gen4, such as the Micron 6500 ION 30.72TB for read-heavy capacity.

Samsung PM1743 vs PM9A3: which should I buy?

This is the Samsung comparison we are asked about most, and the two are not really competitors. The PM9A3 is a Gen4 U.2 read-intensive drive. The PM1743 is Samsung's Gen5 U.3 drive, offered in a read-intensive version and a mixed-use (MU) version. Here is how the listings Nexus Compute carries compare:

• Samsung PM9A3 960GB: PCIe 4.0 x4, U.2, V-NAND TLC, 1 DWPD (read-intensive), up to 6,800 MB/s read and 4,200 MB/s write.
• Samsung PM1743 1.92TB: PCIe 5.0 x4, U.3, V-NAND TLC, 1 DWPD (read-intensive), up to 14,000 MB/s read and 6,750 MB/s write.
• Samsung PM1743 MU 1.6TB: PCIe 5.0 x4, U.3, V-NAND TLC, 3 DWPD (mixed use), with the same rated sequential figures as the read-intensive PM1743.

Choose the PM9A3 for Gen4 servers, U.2 bays, and read-mostly roles where the network or the application sets the speed limit. Choose the PM1743 for a Gen5 server with Gen5 bays and a bandwidth-bound, read-heavy workload. Choose the PM1743 MU when the same server also writes heavily, such as database logs, caching or VM hosts with constant churn: 3 DWPD means the drive is rated for three full-capacity writes per day over its warranty period, against one for the read-intensive models.

The same split exists across brands. The Kioxia CM7-R 1.92TB and Kioxia CM7-V 1.6TB mirror the PM1743 and PM1743 MU at 1 DWPD and 3 DWPD, with the same rated sequential figures. On Gen4, the Micron 7450 PRO 960GB and Kioxia CD8-R 1.92TB are U.3 alternatives to the PM9A3 with the same rated read and write speeds.

Buy Gen5 when the server, the backplane and the workload are all Gen5. If any one of the three is Gen4, buy Gen4 and spend the difference on capacity or endurance.

What should I check before ordering?

• The exact server model and generation, and whether its NVMe bays are rated for Gen5.
• Bay type: U.2, U.3 or E3.S. Do not assume every 2.5-inch NVMe bay takes every 2.5-inch NVMe drive.
• How the drives connect: direct to the CPU, through a tri-mode RAID controller, or through a PCIe switch. The controller path can cap throughput below what the drives can deliver; our guide to RAID vs HBA controllers covers that choice.
• Endurance class matched to the write load: 1 DWPD for read-mostly work, 3 DWPD for mixed use.
• The server vendor's supported-drive list, if you need vendor support on the storage.
• Airflow and fan profile for Gen5 drives in dense chassis.
• Send the server model with your drive list and Nexus Compute will check compatibility before dispatch and quote within 48 business hours.