HP ProLiant DL380p ISS Technology Focus, Number 14 - Page 1
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ISS Technology Focus Number 14 In this issue: » Choose the right solidstate storage solution » Efficiency of DC vs. AC power supplies » Tip: Check HyperThreading status remotely using Microsoft® Windows® PowerShell » Recent publications ISS TechComm iTunes New posts are now available on Apple iTunes, either check your iTunes page or go to ours: iTunes page. Follow us: Like us: Choose the right solid-state storage solution This article describes the features and applications of HP enterprise class solid-state drives (SSDs) and IO accelerators. A subsequent article will detail the differences in these solid-state storage devices based on performance, latency, lifetime writes, and expected life at 100% writes. HP solid-state storage devices are based on NAND flash memory, which is the predominant solid-state storage technology. Before describing the features and applications of these devices, we must explain a few important characteristics of NAND flash memory. If you are unfamiliar with NAND architecture, read the technology brief "Solid state storage technology for ProLiant servers" at http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01580706/c01580706.pdf. NAND flash memory Solid-state devices based on NAND technology have a finite amount of writes and can be „worn out‟ over time. The life expectancy (endurance) of a SSD or IO accelerator is dependent on the NAND technology, write workloads, and the capacity of the device. There are two primary types of NAND flash technology, each with different endurance, performance, densities, and costs. • Single-level cell (SLC) technology works by storing one of two different charge states in each cell, representing a single bit of information. • Multi-level cell (MLC) technology stores two or more bits in one cell. This allows each cell to increase storage density by 100% or more. Two-bit MLC stores one of four different charge states in a cell. Three-bit MLC stores one of eight different charge states in a cell. As shown in Figure 1-1, SLC NAND has higher endurance, retention, and write performance than MLC NAND. MLC technology is the dominant NAND technology used in consumer products where cost is a primary factor. SLC-based SSDs provide the highest performance and endurance for enterprise server storage. MLC-based SSDs provide a lower cost per GB solution but have lower write performance and write endurance. MLCbased SSDs are a good option for read-intensive application environments with limited write requirements.