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Introducing Solid State Drives

Solid State Drives overview

Besides an ever increasing demand for more storage capacity, many businesses constantly
require faster storage performance for their high-end, business critical applications.
The hard disk drive technology has improved dramatically over the years, sustaining more
IOPS and increased throughput while providing higher storage density at a lower price.
However, because of its moving and spinning parts, there are inherent physical limitations to
the response times (access time and latency) that an HDD can achieve.
These limitations and the continuing demand for better response times and more throughput
have created the need for a different storage technology that avoids seeks and rotational
delays. This technology, known as Solid State Drives, can provide access times measured in
microseconds.
Solid State Drives use semiconductor devices (solid state memory) to store data and have no
moving parts. SSDs are in fact not new and have existed for a while. They were initially based
on Dynamic random access memory (DRAM) and often referred to as RAM-disks. Although
they had very good performance, they were also extremely expensive and most businesses
could not justify the cost.

SSD endurance

The life of the flash is limited by the number of write/erase operations that can be performed
on the flash. To extend the lifetime of the drive and to ensure integrity of the data on the drive,
SSDs as used in the DS8000 have built-in dynamic/static Wear-Leveling and Bad-Block
mapping algorithms. This is further complemented by Over-Provisioning and Error Detection
Code / Error Correction Code algorithms to ensure data reliability.
These algorithms are implemented in various electronic components of the drive as
functionally depicted in Figure 4. The algorithms are set at manufacturing and cannot be
tuned by the user.

DS GUI and DSCLI changes

Creating arrays, ranks, extent pools, and volumes based on SSDs is the same process as
with regular disks. Some minor changes were made to some DS GUI panels and DS CLI
commands output to reflect the presence of SSDs in the system. Next, we provide some
illustrations.
Note, however, that even though the process is unchanged, there are special considerations
and best practices to follow when creating arrays, ranks, and volumes if you want to keep the
benefits of SSDs. These considerations and best practices are discussed in “Considerations
for DS8000 with SSDs” on page 11.

Solid State Drives( SSD )

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introduction

The SSD (Solid State Drive) : sometimes improperly referred to as “Solid State Disk or an electric disk” is a data storage device that uses integrated circuit assemblies as memory to store data persistently.
SSD technology uses electronic interfaces compatible with traditional block (I/O) hard disk drives.
SSDs do not employ any moving mechanical components, which distinguishes them from traditional magnetic disks such as hard disk drives (HDDs) or floppy disks, which are electromechanical devices containing spinning disks and movable read/write heads.
Compared with electromechanical disks, SSDs are typically less susceptible to physical shock, are silent, and have lower access time

Development And History

SSD’s using RAM :

The origins of SSDs came from the 1950s and used two similar technologies: magnetic core memory and card capacitor read-only store (CCROS).[These auxiliary memory units, as they were called at the time, emerged during the era of vacuum tube computers. But with the introduction of cheaper drum storage units, their use was discontinued.
In the late 1970s, General Instruments produced an electrically alterable ROM (EAROM) which operated somewhat like the later NAND flash memory. Unfortunately, a ten-year life was not achievable and many companies abandoned the technology.

Architecture & Design

The key components of an SSD are
1: the controller
2: the memory
The primary memory component in an SSD had been DRAM volatile memory since they were first developed, but since 2009 it is more commonly NAND flash non-volatile memory, Other components play a less significant role in the operation of the SSD and vary among manufacturers.

Controller :

Every SSD includes a controller that incorporates the electronics that bridge the NAND memory components to the host computer.
It is one of the most important factors of SSD performance.
Functions performed by the controller Are:
1. Error correction (ECC)
2. Wear leveling
3. Bad block mapping
4. Read scrubbing and read disturb management
5. Read and write caching
6. Garbage collection
7. Encryption

Myths with SSD’s :

Solid state drives are too expensive for mainstream computing
Today, the proven performance of MLC NAND-based SSDs is enabling more consumer-oriented prices. SSDs for notebook computers are most suitable for users who value increased reliability, ruggedness and performance.
All SSDs have similar performance
there can be a significant difference in performance from one SSD to another
SSD capacities are too small
SSDs are now available in many capacities, including high-capacity drives of 256GB and 512GB for mobile computer users.