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SOLID STATE DRIVES
A SEMINAR REPORT
VISHAL K SETTI
in partial fulfillment for the award of the degree of
BACHELOR OF ENGINEERING
ELECTRONICS AND COMMUNICATION ENGINEERING
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ANNA UNIVERSITY CHENNAI
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VISHAL K SETTI
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An enormous shift has take place in technology of storage and complex,
transistors-based devices for primary storage are now increasingly common.
Most people are aware of the transition from portable magnetic floppy discs to
portable USB transistor flash drives, similarly the transition from magnetic IC
hard drives to Solid-State Drives inside modern computers has attracted great
attention from the research community.
A Solid-State Drive is a non-volatile memory system that emulates a
magnetic hard drive. With proper design, an SSD is able to provide high data
transfer rates with low access time.
SSDs adoption will grow as the installed base grows and market
matures. The reliability of SSDs will be exposed for good and bad. Hence, it
is most beneficial for device and system OEMs to define common metrics that
define solid state storage reliability consistently and simultaneously establish
these definitions sooner or later.
So in this seminar, we will be covering elaborately the types, working of
internal components & system as a whole and also the basics about data
storage in Drives. The future of storage is Solid-State Drive and hope to see
great improvement to implement SSDs even faster and reach every one of us.
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TABLE OF CONTENTS
CONTENTS PAGE NO.
3. The problem with today’s Hard disks……………………………….3
4. Comparison: HDD vs SSD ………………………………………….........4
5. Basic components in an SSD …………………………………….........5
6. How Solid State Drives save data ….…………………….............12
7. SSD Types and Form Factors: ……………………………..............13
8. Maintenance of an SSD………………………………………..............15
11. Applications of SSDs……………….…………………………...............19
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Solid state is term that refers to electronic circuitry that is built entirely out of
semiconductors. The term was
originally used to define those
electronics such as a transistor
radio that used semiconductors
rather than vacuum tubes in its
construction. Most all electronics
that we have today are built
around semiconductors and chips.
In terms of a SSD, it refers to the
fact that the primary storage
medium is through semiconductors rather than a magnetic media such as a hard
drive. In fact, you wouldn't even know whether you're using an SSD or HDD if it
wasn't for the differences in how they operate.
HDDs store their data on spinning metal platters, and whenever your
computer wants to access some of that data a little needle-like component (called
the "head") moves to the data's position and provides it to the computer. Writing
data to a HDD works in a similar fashion, where parts are constantly moving.
SSDs, on the other hand, don't move at all. This is a simplified explanation, of
course, but you might have noticed that the SSD's process seems a bit more direct
and efficient. It is, and speed is the primary advantage of an SSD over a traditional
HDD. This makes an SSD the single best upgrade for your computer if you're
looking for a way to make it operate faster.
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Flash memory was invented by Dr. Fujio Masuoka while working for
Toshiba in 1984. The name "flash" was suggested
because the process of erasing the memory contents
reminded him of the flash of a camera. Flash memory
chips store data in a large array of floating gate metal–
oxide–semiconductor (MOS) transistors. Silicon wafers
are manufactured with microscopic transistor dimension,
now approaching 40 nanometers.
The PC hard drive form factor standardized in the
early 1980s with the desktop-class 5.25-inch form factor,
with 3.5-inch desktop and 2.5-inch notebook-class drives coming soon thereafter.
The internal cable interface has changed from Serial to IDE to SCSI to SATA over
the years, but it essentially does the same thing: connects the hard drive to the PC's
motherboard so your data can be processed. Today's 2.5- and 3.5-inch drives use
SATA interfaces almost exclusively (at least on most PCs and Macs). Capacities
have grown from multiple megabytes to multiple terabytes, an increase of millions
fold. Current 3.5-inch HDDs max out at 6TB, with 2.5-inch drives at 4TB max.
The first primary drives that we know as SSDs started during the rise of net
books in the late 2000s. In 2007, the OLPC XO-1 used a 1GB SSD, and the Asus
EEE PC 700 series used a 2GB SSD as primary storage. The SSD chips on low-end
EEE PC units and the XO-1 were permanently soldered to the motherboard. As net
books, ultra books, and other ultra portables became more capable, the SSD
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capacities rose, and eventually standardized on the 2.5-inch notebook form factor.
This way, you could pop a 2.5-inch hard drive out of your laptop or desktop and
replace it easily with an SSD. Other form factors emerged, like the mSATA
miniPCI SSD card and the DIMM-like SSDs in the Apple MacBook Air, but today
many SSDs are built into the 2.5-inch form factor.
The Problem With Today’s Hard Disks
Processors have increased in speed by orders of magnitude over the years.
But spinning hard disk drives (HDD) have not. Performance gap between how fast
processors demand data and how quickly HDD responds. HDD speed lags behind
processors because it is constrained by physical components. So, here the SSDs
come into play.
SSDs are integrated with a cache using non-volatile Flash memory. Flash
memory buffer can speed up repeated reads from the same location. Compared to
normal HDD speed of data access and consequent faster computer boot process,
decreased power consumption, and improved reliability.
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Comparison: HDD vs SSD
Speed HDD has higher latency,
longer read/write times, and
supports fewer IOPs (input
output operations per
second) compared to SSD.
SSD has lower latency,
faster read/writes, and
supports more IOPs (input
output operations per
second) compared to HDD.
Components HDD contains moving parts
- a motor-driven spindle that
holds one or more flat
circular disks (called
platters) coated with a thin
layer of magnetic material.
Read-and-write heads are
positioned on top of the
disks; all this is encased in a
SSD has no moving parts; it
is essentially a memory
chip. It is interconnected,
integrated circuits (ICs)
with an interface connector.
There are three basic
components - controller,
cache and capacitor.
Defragmentation The performance of HDD
drives worsens due to
they need to be periodically
SSD drive performance is
not impacted by
defragmentation is not
Heat, Electricity, Noise Hard disk drives use more
electricity to rotate the
platters, generating heat and
Since no such rotation is
needed in solid state drives,
they use less power and do
not generate heat or noise.
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Dealing with vibration The moving parts of HDDs
make them susceptible to
crashes and damage due to
SSD drives can withstand
vibration up to 2000Hz,
which is much more than
Basic Components In An SSD
SSDs are comprised of a few different main components:
• SSD Controllers:
Every SSD includes a controller, just as a HDD does, which incorporates
the electronics that bridge the NAND memory components to the host computer.
The controller is an embedded processor that executes firmware-level code and
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is one of the most important factors of SSD performance. There are numerous
circuits and programming required for the operation of the device. Some of the
functions performed by the controller include encryption and compressing data
before it is written to the drive as well as:
» Read And Write Disturbs: The act of reading from or writing to a cell can
cause adjacent cells to change state. This is known as bit-flop and has to be
monitored for each read and write.
» Error Correcting Code (ECC): Used to insure that data read, written or
stored has not been unintentionally altered.
» Invalid Block Management: Blocks that contain cells that are not capable of
properly storing data must be mapped out of the user accessible memory
range before data is stored. The blocks also need to be tracked for the life of
» Power data protection: Needed to guard against the involuntary
program/erase of cells during power transitions.
» Garbage Collection: Optimize free space to reduce erase before program
» Wear Levelling: Blocks are monitored for the number of write cycles that
have been performed. The blocks are reused in an ascending order starting
with the blocks that have gone through the fewest write cycles.
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Most SSDs use NAND flash memory because of the lower cost compared to
DRAM. Flash memory SSDs are slower than DRAM SSDs which are mostly used
in enterprise applications and not available to the consumer market.
» Types of Flash Memory:
There are two types of flash memory, NAND and NOR. The names refer to the
type of logic gate used in each memory cell. (Logic gates are a fundamental
building block of digital circuits). Both contain cells -- transistors -- in a grid, but
the wiring between the cells differs.
In NOR flash, the cells are wired in parallel. In NAND flash, the cells are wired in
a series. Because NOR cells contain more wires, they're bigger and more complex.
NAND cells require fewer wires and can be packed on a chip in greater density.
» NAND Flash Memory :
NAND flash memory is a type of non-volatile storage technology that does
not require power to retain data. This is the equivalent of a HDD's platters. NAND
flash was introduced by Toshiba in 1989. NAND flash has found a market in
devices to which large files are frequently uploaded and replaced. MP3 players,
digital cameras and USB drives use NAND flash. An important goal of NAND
flash development has been to reduce the cost per bit and increase maximum chip
capacity so that flash memory can compete with magnetic storage devices like hard
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disks. New developments in NAND flash memory technology are making the chips
smaller, increasing the maximum read-write cycles and lowering voltage demands.
» NAND Flash Unit:
Tunnelling is used to alter the placement of electrons in the floating gate. An
electrical charge is applied to the floating gate.
The charge enters the floating gate and drains to a
ground. This charge causes the floating-gate
transistor to act like an electron gun. The excited
electrons are pushed through and trapped on other
side of the thin oxide layer, giving it a negative
These negatively charged electrons act as a barrier between the control gate
and the floating gate. A special device called a cell sensor monitors the level of the
charge passing through the floating gate. NAND flash memory uses floating gate
MOSFET transistors. Their default state is when the charge is over the 50%. If the
flow through the gate is above the 50% threshold, it has a value of 1. When the
charge passing through drops below the 50% threshold, the value changes to 0. 0's
are data, 1's are erase - the fundamental laws of MLC NAND dictate this.
• Types of NAND:
1. Single-level Cell (SLC) NAND: SLC NAND can store only one data bit per
NAND flash cell. This leads to faster transfer speeds, higher cell endurance,
and lower power consumption.
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The downside to SLC chips used in SSDs is the manufacturing cost per
megabyte and total capacity which is less per NAND cell than MLC. SLCs
are intended for the high-end consumer and
server market and they have approximately 10
times more endurance compared to MLC.
2. Multi-level Cell (MLC) NAND : MLC NAND
stores two bits per NAND flash cell. Storing
more bits per cell achieves a higher capacity
and lower manufacturing cost per megabyte.
MLC SSDs are designed for the mainstream
consumer market and are much faster
compared to standard hard disk drives. MLC
SSDs are improving with faster and more
efficient technologies and are being adopted into the high-end consumer and
3. Endurance Multi-level Cell (eMLC) NAND : eMLC NAND is basically
more expensive MLC flash with better endurance.
4. Triple Level Cell (TLC) NAND : TLC NAND stores three bits per cell.
However P/E cycles for TLC NAND is significantly lower than that of MLC
• Cache or Buffer:
A flash-based SSD typically uses a small amount of DRAM as a cache,
similar to the cache in hard disk drives. A directory of block placement and wear
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levelling data is also kept in the cache while the drive is operating. Data is not
permanently stored in the cache. Most manufacturers do not use an external DRAM
cache on their designs, but still achieve very high performance. Eliminating the
external DRAM enables a smaller footprint for the other flash memory components
in order to build even smaller SSDs.
• Battery or super capacitor:
Another component in higher performing SSDs is a capacitor or some form
of battery. These are necessary to maintain data integrity such that the data in the
cache can be flushed to the drive when power is dropped; some may even hold
power long enough to maintain data in the cache until power is resumed. In the
case of MLC flash memory, a problem called lower page corruption can occur
when MLC flash memory loses power while programming an upper page. The
result is data written previously and presumed safe can be corrupted if the memory
is not supported by a super capacitor in the event of a sudden power loss. This
problem does not exist with SLC flash memory.
• Host Interface:
The host interface is not specifically a component of the SSD, but it is a key part of
the drive. The interface is usually incorporated into the controller. The interface is
generally one of the interfaces found in HDDs.
1. Serial ATA(SATA): The SATA interface is best seen in the left photo
above and consists of a gold connector which easily connects to your
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laptop or desktop computer. Without belabouring on the definition and
revisions of SATA, the consumer only really needs to understand that all
SATA SSDs are backward and forward compatible and any will serve the
purpose it is intended without question. Most computer systems in use are
SATA 2 with newer systems now released with SATA 3 capability.
The difference between the two breaks down to how fast the data can
be transferred from the SSD to your computer and, in the case of
applications, executed. Typically, a SATA 2 SSD will only transfer speeds
as fast as 280 megabytes per second (MB/s) whereas new SATA 3 drives
are reaching as high as 550MB/s in a single form factor notebook or
desktop SATA 3 SSD.
Other types include:
2. M.2 SATA
3. M.2 NVMe
4. PCI Express
• SSD Processor:
The SSD processor (or controller is it is more commonly referred to) is the
heart and soul of the SSD. It is the
engine by which information is
pulled from storage, translated and
then sent to the SATA interface for
travel to your computer system. It is
the sole reason that a typical SSD is
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5-6 times faster than a hard drive in data travel and also the reason that we see a
starting point of about a 90x increase in the information retrieval (disk access) from
an SSD as compared to that of a hard drive.
How Solid-state Drives Save Data
On the outside, solid-state drives look just like HDDs. They're
rectangular in shape, covered in a brushed-metal shell and sized to match
industry-standard form factors for hard drives -- typically 2.5 and 3.5 inches
(6.4 and 8.9 centimeters). But beneath the silver exterior, you'll find an array
of chips organized on a board, with no magnetic or optical media in sight.
Much of that stuff could fit into a smaller space, but SSD manufacturers dress
up their components in extra "housing" to make sure they fit into existing
drive slots of laptops and desktop PCs.
The NAND flash of a solid-state drive stores data differently. Recall that
NAND flash has transistors arranged in a grid with columns and rows. If a
chain of transistors conducts current, it has the value of 1. If it doesn't conduct
current, it's 0. At first, all transistors are set to 1. But when a save operation
begins, current is blocked to some transistors, turning them to 0. This occurs
because of how transistors are arranged. At each intersection of column and
row, two transistors form a cell. One of the transistors is known as a control
gate, the other as a floating gate. When current reaches the control gate,
electrons flow onto the floating gate creating a net positive charge that
interrupts current flow. By applying precise voltages to the transistors, a
unique pattern of 1s and 0s emerges.
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SSD Types and Form Factors:
• Notebook 2.5″ SSDs
The 2.5″ SSD is the most popular size solid state drive and will fit into just
about any consumer PC, given exception new ultrabook designs which are just too
thin to house anything but a mSATA SSD as it is only as
think as a 25 cent piece. Notebook SSDs have become so
popular, in fact, that most manufacturers don’t even sell the
larger and much heavier 3.5″ desktop size, choosing instead
to include a 2.5″ to 3.5″ adapter with their notebook SSD kits.
The notebook SSD is available in either SATA 2 or
SATA 3 which means that performance speeds as high as
285MB/s (SATA 2) and 550MB/s (SATA 3) are possible. It
is an important to consider that buying a SATA 3 SSD serves no purpose if your
laptop (or desktop) only supports SATA 2 as 95% of those on the market presently
• Super Slim 2.5″ Ssd Design
The normal consumer SSD available today
has dimensions of approximately 69mm wide
x100mm long x 9.5mm thick. One of the first solid
state drives released, the Intel X25m, was actually
a superslim SSD and they have recently followed
suit with the Intel 320 Series SSD, both of which
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are only 7mm thick with a black adapter that allows their fit in typical notebooks.
• mSATA SSDs
The mSATA SSD measures about 50mm long x 30mm wide x 4.85mm thick.
The size of this SSD is key to its present surge into the ultrabook market. mSATA
SSDs are now being found in ultrabooks such as
the Samsung Series 9 and Toshiba Z830 that we
have reviewed as well as some larger notebooks
manufactured by Dell. They use a modified
mPCIe (mini PCI express) interface and are
typically SATA 2 although we are now seeing
SATA 3 entries by Runcore, Samsung and AData.
• Solid State Modules:
Flash memory chips reside in a dual in-line memory module (DIMM) or similar
form. They may use a standard HDD interface like SATA.
The M.2 standard provides higher performance and capacity while
minimizing module footprint. M.2 modules connect either via SATA or PCIe,
come in multiple widths and lengths, and are available in soldered down or
connectorized type, and can have single or double-sided components. All soldered
down modules are single-sided and are intended to be used in low-profile
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» M.2 NVMe SSDs
They fit into a PCIe 3.0 x4 slot, offer up to 1 TB
capacity, and deliver a bandwidth of up to 32 Gb/s (8
Gb/s per lane), which is four to six times the data transfer
speed of the previous-generation AHCI protocol on Serial
» M.2 SATA SSDs
These deliver high-performance SATA 6 Gb/s and adopt
the double-sided configuration to enable higher densities.
They come in three sizes: 2242, 2260 and 2280.
Maintenance Of An SSD
Basically SSDs maintain themselves. There are many things that SSD
manufactures do to make sure the drive lasts like over provisioning, having garbage
collection, and wear leveling built into the drive. Let’s talk about the main points of
what an SSD does to maintain itself. In a nutshell, all SSDs have garbage
collection. TRIM simply optimizes it. It is not needed, but preferred to have
enabled as it reduces write amplification and speeds up garbage collection. Garbage
collection (GC) is a fundamental process with all SSDs, but it can be implemented
in different ways that can impact the overall SSD performance and endurance.
Unlike hard disk drives (HDDs), NAND flash memory cannot overwrite
existing data they must first erase old data before writing new data to the same
location. With SSDs, GC is the name for the process of relocating existing data to
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new locations and allowing the surrounding invalid data to be erased. Flash
memory is divided into blocks, which is further divided in pages. Data can be
written directly into an empty page, but only whole blocks can be erased.
Therefore, to reclaim the space taken up by invalid data, all the valid data from one
block must be first copied and written into the empty pages of a new block. Only
then can the invalid data in the original block be erased, making it ready for new
valid data to be written.
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1. Faster than hard disk drives: Because an SSD has no mechanical parts, it is
considerably faster than an HDD. This is one of the advantages of a solid-state
drive. Fragmentation of data in a solid-state drive is negligible unlike in a hard disk
drive making it inherently faster. An SSD is 25 to 100 times faster than a typical
HDD. This translates to faster boot times, quicker file transfers, and greater
bandwidth for enterprise computing.
2. Low power consumption An SSD has no moving parts and it does not require
mechanical work to become operational. This low power consumption gives solid-
state drives another advantage. This means that an SSD is suitable for energy
efficient computers and consumer electronic devices. Furthermore, using a solid-
state drive lessens that susceptibility of a computer or device to overheat.
3. Durable than hard disk drives: Because an SSD has no moving or mechanical
parts, it is more durable to drops and shudders thereby making it more resilient
against data loss caused by physical or external trauma.
4. No noise while in operation: The absence of a rotating metal platter to store
data and a moving read arm makes an SDD completely quiet while in operation.
5. Compact than hard disk drives: An SSD is considerably compact than HDD
because of the absence of mechanical or movable parts. This also means that a
solid-state drive is a more suitable or advantageous storage component for portable
consumer electronic devices such as ultrabooks and tablets.
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1. More expensive than hard disk drives: An SSD is more expensive than an
HDD in terms of dollar per GB. This is one of the primary disadvantages of a solid-
state drive. Compared with a hard disk drive, a solid-state drive with a similar
storage capacity can be twice as expensive. This translates to more expensive
computers or other devices with solid-state drive systems than those that have hard
2. Limited storage capacity: Current SSDs in the market have limited storage
capacity. Computers or devices with an SSD storage system usually have a base
storage capacity of 128GB. Higher storage capacity contributes to the overall price
of a computer or device. Although there are solid-state drives with a capacity of
4TB, they are very rare and expensive.
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3. Shorter lifespan than hard disk drives: An SSD has a limited write cycle. The
flash memories of a solid-state drive can only be used for a finite number of writes.
An SSD cannot write a single bit of information without first erasing and then
rewriting very large blocks of data at one time. As each cell goes through this
cycle, it becomes more useless. However, this decaying process does not affect the
read capability of the entire SSD.
Applications of SSDs
Initially Solid State Drives (SSDs) were designed for consumer devices. With the
increased speed and power, various other sectors also came with a huge demand for
them. Some are discussed below:
1. Business – Companies depending on programming environments or data
analysis often rely on SSDs, as access times and file-transfer speeds are
2. Gaming – For every gaming program the computer requires a faster data
access speed enabling a faster load time which is provided by the SSD.
3. Smartphone – With the continuous developments in Smartphone industry,
the need for small sized fast memory is best fulfilled by SSD.
4. Servers – SSDs can improve the server’s response time due to its speed. They
are suitable for faster read and write operations.
5. Smart Wearable & Gadgets – The lesser space requirement, low power
consumption and high speed makes it an indispensable part of Smart
Wearable and Gadgets.
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It is a very visible upgrade from a hard drive system and renders
a great deal more enjoyment as well as productivity at the end of the
day. Upgrading your regular old hard drive to a solid-state drive is
one of the best upgrades you can make to your computer nowadays,
as our hard drives tend to be among the biggest bottlenecks in
performance. Understanding the different types of SSDs can, not only
help you out in your understanding of such, but also, can better equip
and help save a great deal of money in your final purchase decision.
So, is SSD worth It? In high performance environments, yes.
Because SSD form factors are the same as HDDs, replacing disk with
SSDs is not a major technology refresh. And because of their higher
performance and falling prices, SSDs continue to be a highly
competitive storage media in the data center.
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