Samsung's PM853T and 845DC EVO have helped dispel the stigma surrounding 3-bit MLC (TLC) NAND in the datacenter. 3-bit MLC has endurance limitations, but with the correct engineering and firmware expertise, it is fully capable of addressing read-centric workloads in the datacenter. Coupling cost-effective 3-bit MLC NAND with enterprise-grade features creates a solution that all but displaces the relatively old practice of using client SSDs as a value-tier in the datacenter.
The OEM specific PM853T is very similar to its retail branded sibling, the : 845DC EVO. While there are a few key differentiators between the two, they are both powered by Samsung 19nm 3-bit MLC, and available in capacity points of 240, 480, and 960GB in a 7mm form factor. Both SSDs also offer power loss protection via Tantalum capacitors - a crucial requirement in datacenter environments.
The differences become clear when we look at the performance specifications. The 6GB/s SATA PM853T features datacenter-optimized firmware that delivers a slightly higher random 4k write performance of 15,000 IOPS, but delivers the same blistering 87,000 IOPS performance in random read workloads. The read performance of both Samsung SSDs easily outpaces competitors in the same class. Both Samsung SSDs offer up to 530 / 410 MB/s of sequential read/write performance, meeting or beating other competitors in the same class.
The PM853T has a slightly more conservative endurance rating of 0.3 DWPD (Drive Writes per Day) in comparison to the 845DC EVO with 0.35 DWPD. Endurance varies by workload, and the 0.3 DWPD metric represents pure random write workloads, which aren't really the intended workload for a read-centric SSDs. In sequential workloads, the PM853T can extend endurance up to 1.6 DWPD, but in many real-world deployments, the actual endurance will likely fall in the middle. Careful analysis of the workload, and possible user adjustments of overprovisioning, can allow users to deploy the PM853T into a wide range of applications. It is important to note that the DWPD measurements are for five years, while the warranty period is for three years. The three-year warranty of the 845DC EVO is standard for OEM applications.
The PM853T offers a lower UBER rating of one per 10^16, in comparison to the one per 10^17 from the 845DC EVO. The 845DC EVO offers a two-million hour MTBF, but the PM853T steps back to 1.5 million hours. These more conservative specifications may be the result of variations in firmware, or a more stringent specification process for the OEM market.
The PM853T also extends the same focus on performance consistency we have seen with other Samsung offerings by specifying 99.9% read latency QoS at 200us, and 400us for write latency. Samsung continues to leverage their vertical-integration advantage by utilizing the Samsung MEX controller, and 1GB of Samsung's own LPDDR2 cache. Samsung has deployed the MEX controller extensively in both client and enterprise applications.
The PM853T aims to provide the same winning performance of higher endurance SSDs, at the lower price point enabled by 3-bit MLC NAND. Let's see how it holds up in our testing.
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- Page 1 [Introduction]
- Page 2 [Samsung PM853T Internals and Specifications]
- Page 3 [Test System and Methodology]
- Page 4 [Benchmarks - 4k Random Read/Write]
- Page 5 [Benchmarks - 8k Random Read/Write]
- Page 6 [Benchmarks - 128k Sequential Read/Write]
- Page 7 [Benchmarks - Database/OLTP and Web Server]
- Page 8 [Benchmarks - Email Server]
- Page 9 [Final Thoughts]