ISS Technology Focus, Number 14

ISS Technology Focus
Number 14
In this issue:
»
Choose the right solid-
state storage solution
»
Efficiency of DC vs. AC
power supplies
»
Tip: Check Hyper-
Threading status
remotely using
Microsoft® Windows®
PowerShell
»
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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. MLC-
based SSDs are a good option for read-intensive application environments with limited
write requirements.

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