This document summarizes a seminar presentation on solid state drives (SSDs). It introduces SSDs and discusses their memory types, form factors, architecture, and components. It compares SSDs to hard disk drives in terms of startup speed, technical specifications, advantages, and disadvantages. The document outlines SSD maintenance concepts like garbage collection and trim and discusses SSD applications before concluding.

1. Seminar on SSDs
Presented By:
RB
Roll Number : 11-***
Seat Number : 6***9
Under the Guidance of :
Prof. Sachin Bojewar

2. Contents
 Introduction,Key Terms
 SSD Memory Types
 Form Factor and Types
 Architecture,Components & Function
 SSD vs HDD – Start-Up Test
 Technical Comparison of SSD & HDD
 Advantages
 Disadvantages
 SSD Maintenance Key Concepts
 SSD Applications
 Conclusion

3. Introduction
 Solid state is term that refers to electronic circuitry that is built entirely
out of semiconductors.
 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 1995, M-Systems introduced first flash-based solid-state drives.
 A Solid-State Drive (SSD) is a data storage device that uses solid state
memory to store persistent data and SSDs use same I/O interfaces
developed for hard disk drives.

4. Key Terms
MTBF - Mean time between failures - in other words, how long it takes between one
data failure and the next on your HDD or SSD. Data failures occur far more frequently
on HDDs than on SSDs.
SATA - Serial Advanced Technology Attachment. It's a type of interface that connects a
storage device or optical drive to your computer's motherboard.
SATA is measured by how fast data transfers to/from the device. There are three SATA
speeds, SATA I (1.5Gb/s), SATA II (3.0Gb/s) and SATA III (6.0Gb/s).
Lithography – It refers to the semiconductor manufacturing technology in nanometer
(nm) used to manufacture the processor (usually 19-50 nm for SSDs).
Flash Translation Layer - is a software layer used in computing to support normal file
systems with flash memory. FTL is a translation layer between the sector-based file
system and NAND flash chips. It enables the operating system and file system access
NAND flash memory devices as access disk drives.
IOPS - IOPS (Input/Output Operations Per Second, pronounced eye-ops) is a common
performance measurement used to benchmark computer storage devices like hard
disk drives (HDD), solid state drives (SSD), and storage area networks (SAN).

5. SSD - Memory Types
Flash memory-based SSDs:
 Use non-volatile NAND flash memory
 Ability to retain the data without a constant power supply
 lower cost compared to DRAM
 Flash memory SSDs are slower than DRAM solutions.
DRAM-based SSDs:
 Based on volatile memory such as DRAM
 internal battery or an external AC/DC adapter is needed to hold the data
 ultrafast data access
 primarily to accelerate applications
 Higher cost compared to NAND flash memory

6. Types of Flash Memory
There are two types of flash memory - NAND (1989i) and NOR (1988t).
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.
As a result, NAND flash is less expensive, and it can read and write data
much more rapidly.
This makes NAND flash an ideal storage technology and explains why it's the
predominant type of memory in solid-state drives.
NOR flash is ideal for lower-density, high-speed, read-only applications, such
as those in code-storage applications.

7. Why NAND?
• Most SSD manufacturers use non-volatile NAND flash memory in the
construction of their SSDs because of the lower cost compared with DRAM
and the ability to retain the data without a constant power supply,
ensuring data persistence through sudden power outages.
• Flash memory SSDs are slower than DRAM solutions, and some early
designs were even slower than HDDs after continued use. This problem
was resolved by controllers that came out in 2009 and later
• 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 leveling data is also kept in the
cache while the drive is operating. Data is not permanently stored in the
cache.

8. NAND
• 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 is erase - the fundamental laws of MLC NAND dictate this.
You only write the 0's when you write data to NAND.
So in an erased state the NAND has to report a 1.
NAND manufactures include:
Micron Technology, Inc.,Intel Corporation,Hynix Semiconductor,Phison
Electronics Corp.,SanDisk Corporation,Toshiba,Samsung

11. Types of NANDs used in SSDs
• 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. 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.
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
server markets.
Endurance Multi-level Cell (eMLC) NAND - eMLC NAND is basically more
expensive MLC flash with better endurance.

12. SLC v/s MLC
• SLC (Single Layer Cell) - highest performance, at a very high cost,
enterprise grade NAND
~ 90-100,000 program/erase cycles per cell (highest endurance)
- lowest density (1 bit per cell, lower is better for endurance)
- lower power consumption
- faster write speeds
- much higher cost (3 times higher than MLC)
- good fit for industrial grade devices, embedded systems, critical
applications.
MLC (Multi Layer Cell) - average performance, consumer grade NAND
~ 10,000 program/erase cycles per cell
- higher density (2 bits per cell)
- lower endurance limit than SLC
- lower cost (3 times lower than SLC)
- good fit for consumer products. Not suggested for critical applications
which require frequent updates of data

13. TLC
• TLC (Three Layer Cell) - lower performance, lowest cost NAND
~ 3-5,000 program/erase cycles per cell
- highest density (3 bits per cell)
- lower endurance limit than MLC and SLC
- best price point (30% lower than MLC)
- somewhat slower read and write speed than MLC
- good fit for lower-end consumer products. Not recommended for critical
applications which require frequent updating of data
Generally, SLC drives are the fastest, most relieble and most expensive
drives available, usually used in the enterprise because of their
consiredably higher cost. Both MLC and TLC are widely used consumer
grade memory, with MLC being better in terms of endurance.

14. Program/Erase (P/E Cycle)
• In NAND flash, storage is achieved using floating-gate transistors that form
NAND gates. As such, the non-programmed state of a bit is 1, while the
programming operation injects charge into the floating gate and its
resultant bit becomes 0. The opposite operation, erase, extracts the stored
charge and reverts the state to 1. MLC flash increases density by storing
multiple levels of charge in one cell, at the expense of decreased reliability
and endurance. Thus, reading bytes from a non-programmed or erased
area will return FF. The erase and program operations inherently cause
degradation of the oxide layer isolating the floating gate; this is the reason
for NAND flash's finite lifespan (100K-1M erase/program cycles for SLC
typically, 2.5K-10K erase/program cycles for MLC) and data retention time.

15. Usage of MLC v/s SLC
• Lower priced drives usually use multi-level cell (MLC) flash memory, which
is slower and less reliable than single-level cell (SLC) flash memory.
This can be mitigated or even reversed by the internal design structure of
the SSD, such as interleaving, changes to writing algorithms,and higher
over-provisioning (more excess capacity) with which the wear-leveling
algorithms can work.
• Higher priced SSDs usually use single-level cell NAND; these drives are
usually used for enterprise applications due to better durability.

16. Comparison

17. Definition
• Armed with this information, we can offer a more precise definition of a
solid-state drive:
It's a device that uses NAND flash to provide non-volatile, rewritable
memory.
In computers, a solid-state drive can be used as a storage device, replacing
the traditional hard disk drive.

18. Form Factor and Types
 Standard HDD form factors
 Box form factors
 M-SATA
 PCI-e
 Dual-Hybrid and SSHDs

19. Standard
 Standard HDD form factors use SATA II or III – is equal to size of traditional HDD form
factors like 3.5", 2.5”
2.55’’ HDD form factor

20. Box Form
 Box form factors – mainly used by DRAM based SSDs ,as they need external power
supply or battery pack.
Box form factor

21. mSATA SSDs
 The mSATA (mini-SATA) SSD measures about 50mm long x 30mm wide x 4.85mm
thick, or 1/3 the size of a business card. The size of this SSD is key to its present
surge into the ultrabook market.Uses mPCIe (mini PCI express) interface.

22. PCIe SSDs
• . PCIe (PCI Express (Peripheral Component Interconnect Express) SSD can be had
for less than $700 and reaches performance speeds as high as 1.5GB/s.
v2.x: 500 MB/s (5 GT/s) v3.0: 985 MB/s (8 GT/s)

23. Dual-drive Hybrid and SSHDs
• Hybrid drives are storage devices that combine NAND flash solid-state
drive (SSD) with hard disk drive (HDD) technology, with the intent of
adding some of the speed of SSDs to the cost-effective storage capacity of
traditional HDDs. The purpose of the SSD in a hybrid drive is to act as a
cache for the data stored on the HDD, by keeping copies of the most
frequently used data on the SSD for improved overall performance.

24. WD Black SSHD

25. Components
Block Diagram

27. 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
discussed above. The interface is generally one of the interfaces found in
HDDs. They include:
• Serial attached SCSI - SAS (generally found on servers, >3.0 Gbit/s)
• Serial ATA - SATA (>1.5 Gbit/s)
• PCI Express - (>2.0 Gbit/s)
• Fibre Channel (almost exclusively found on servers, >200 Mbit/s)
• USB - (> 1.5 Mbit/s)
• Parallel ATA (IDE, >26.4 Mbit/s) interface (mostly replaced by SATA)
• (Parallel) SCSI (generally found on servers; mostly replaced by SAS; last
SCSI-based SSD introduced in 2004, >40 Mbit/s)

28. Controller
 The controller is an embedded processor and executes firmware-level code is
one of the most important factors of SSD performance.
There are numerous circuits and programming required for the operation of the
device.
Functions:
 Error Correcting Code (ECC)
 Wear leveling
 Bad block mapping
 Read And Write Disturbs
 Garbage collection
 Encryption
 Power Data Protection

29. SSD Developers
• Some common SSD controller developers include:
– Samsung
– Marvell
– SandForce (Now owned by LSI) - SandForce controllers are the only
devices with a compression algorithm in real time. Basic, it
minimizes the impact of specific submissions on the Flash.
– Toshiba
– Indilinx (owned by OCZ.)
– Intel
– JMicron

30. How SSDs are MADE
Crucial’s Video

31. Technical Comparison of SSD & HDD
Solid-state Drive Hard disk drive
Random access time
Typically under 0.1 ms
Random access time
Ranges from 2.9 (high end server drive) to 12
ms (laptop HDD) due to the need to move
the heads and wait for the data to rotate
under the read/write head
Read latency time
Very low,but degrades over time
Read latency time
high
100MB/s to 600MB/s 50MB/s to 140MB/s. (4200-15000 RPM)
High Reliability and Startup Time
SSDs have no moving parts to fail
mechanically. Doubles with size.
Low Reliability and Startup Time
HDDs have moving parts and are subject to
sudden failure
Small and light in weight. Relatively large and heavy
Size Upto 2 TB HDDs of up to 6TB are available.
Power Consumption : Around 2 W Power Consumption : 0.35 to 20 W
Cost : As of April 2014 – 0.45$/GB Cost : HDDs cost about US$0.05 per GB for
3.5-inch and $0.10 per GB for 2.5-inch drives.

32. Technical Comparison of SSD & HDD
Solid-state drive Hard disk drive
Noise Free except for Electric Noise from
Circuits
HDDs have moving parts (heads, actuator,
and spindle motor) and make characteristic
sounds of whirring and clicking; noise
levels vary between models, but can be
significant (while often much lower than
the sound from the cooling fans). Laptop
hard disks are relatively quiet.
Life Span : More reliable due to improved
technology.5-10 Years.
Life Span : Relatively Less Reliable – Avg 6
Years.
Expected 9-11 Years.
100MB/s to 600MB/s 50MB/s to 140MB/s. (4200-15000 RPM)
Read and Write Speeds are almost similar for
High Performance SSDs
HDDs generally have slightly lower write
speeds than their read speeds.
Affected by Free Blocks, hence it needs TRIM Not affected by free blocks and do not
benefit from TRIM

36. SSD vs HDD - Start-Up Speed Test
➔ This video shows the speed difference between a solid state drive and
standard hard drive on a Windows 7 PC.

37. Advantages
 High performance – siginificantly faster than a standard HDD
 Faster seek time – upto 60x faster than HDD
 Highly durable – no moving parts,can withstand 1500Gs
operating shock
 Lower power – Lesser power consuption ,cooler operation
 Silent operation – ideal for post production enviornments
 Lighter weight – perfect for portable devices
 Wider operating Temp. - 0c – 70c
 Best Upgrade for your system (83 milllion units sold in 2013!)
 Indexing,Fragmentation not required.

38. Disadvantages
 They are more expensive than traditional hard drives.
 They currently offer less storage space than traditional hard
drives.
 Slower Write Speed on low-end Models(MLC based types)
 Reliability varies significantly across different SSD
manufacturers and models with return rates reaching 40%
for specific drives.
 Not all drives are able to survive multiple power outages.

39. MAINTENANCE OF AN SSD
Basically they 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.

40. Garbage Collection
• Optimize free space to reduce erase before program operations.
• With SSDs, GC is the name for the process of relocating existing data to
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.

41. TRIM Command
• In computing, a TRIM command allows an operating system to inform a
solid-state drive (SSD) which blocks of data are no longer considered in
use and can be wiped internally
• The advantage of the TRIM command is that it enables the SSD’s GC to
skip the invalid data rather than moving it, thus saving time not rewriting
the invalid data.
• This results in a reduction of the number of erase cycles on the flash
memory and enables higher performance during writes. The SSD doesn’t
need to immediately delete or garbage collect these locations it just marks
them as no longer valid.
• TRIM can be initiated in Windows by actions such as emptying the Recycle
Bin, but the SSD must also execute the command.
OSes that support TRIM include:
• Win 8/8.1,Win 7,Linux distros since 2010,Mac OSX lion

42. Wear Leveling
• 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.
• NAND flash memory is susceptible to wear due to repeated program and
erase cycles that are commonly done in data storage applications and
systems using Flash Translation Layer (FTL).
• Constantly programming and erasing to the same memory location
eventually wears that portion of memory out and makes it invalid. As a
result, the NAND flash would have limited lifetime. To prevent scenarios
such as these from occurring, special algorithms are deployed within the
SSD called wear leveling.
• As the term suggests, wear leveling provides a method for distributing
program and erase cycles uniformly throughout all of the memory blocks
within the SSD. This prevents continuous program and erase cycles to the
same memory block, resulting in greater extended life to the overall NAND
flash memory.

43. Overprovisioning
• Over provisioning is a technique used in the design of flash
SSDs and flash media cards. By providing extra memory
capacity (which the user can't access) the SSD controller can
more easily create pre-erased blocks ready to be used in the
virtual pool. Overprovisioning improves:
1. Write performance and IOPS
2. Reliability and Endurance
When an SSD is almost full, this could cause problems. Even for
writing a small amount of data you need a completely empty
block. For this reason SSDs have over-provisioning, which means
more storage capacity present than is available.

44. Endurance Management
• The use of an endurance management algorithm ensures that sufficient
Program/Erase (P/E) cycles are available for the warranty time period of
the drive.
• The firmware will limit writes if a drive is written heavily. However,
customers will rarely see performance throttling when an SSD is used
under the intended application.

45. SSD Applications
 Servers (Enterprise Applications)
 Desktop computers,Laptops,Ultrabooks
 Embedded Systems
 HD Camcorders
 Smart TVs
 CCTV Digital Video
Recorder (DVR)
 Set-Top Boxes
 Gaming Consoles

46. SSD Applications
OLTP -> Online transaction processing
DSS -> Decision Support System (DSS)
HPC -> High-performance computing

47. SSD Applications
Enterprise Drives
Enterprise flash drives (EFDs) are designed for applications requiring high
I/O performance (IOPS), reliability, energy efficiency and, more recently,
consistent performance.
In most cases, an EFD is an SSD with a higher set of specifications,
compared with SSDs that would typically be used in notebook
computers.
The term was first used by EMC in January 2008, to help them identify
SSD manufacturers who would provide products meeting these higher
standards.

48. Sequential Read 500 MB/s
Sequential Write 365 MB/s
Random Read (100% Span) 75000 IOPS
Random Write (100% Span) 32000 IOPS
Cost : 470$ Approx ~ 28K INR
MTBF – 2 Million Hrs

49. SSDs in Hybrid Pool
The purchase cost of the drives is a 67 percent savings (US$55,000 versus
US$18,000).
The amount of electricity consumed provides a 66 percent savings (1.2 kilowatts
versus 0.392 kilowatts)

50. SSD Applications
• Small boot drive: (~64GB) - With a 64GB drive you get ~59.6GB of
formatted space. With a 60GB drive you get ~55.9GB of space. If you
want to install the OS, all the programs that you want, and a game or
two, then a 60/64 GB SSD will do.
• Medium sized boot drive: (~128GB) - With a 128GB drive you get
~119.24GB of formatted space. With a 120GB drive you get ~111.79GB
of space. If you want to install the OS, all the programs that you want, a
few games and a 120/128GB SSD at least is recommended.
• Large boot drive: (~256GB+) - If you want to have Steam or most/all of
your games or other large items on your SSD at least a 240/256 GB SSD
is recommended.
DESKTOP/LAPTOPS/ULTRABOOKS -> One thing to notice is that with
most 60/64GB SSDs is that their 120/128GB and larger counterparts
usually have twice the lifespan.

51. SSD Applications

52. Conclusion
 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.
 Increase in storage, options,availability,durability and
decrease in price.
 Quicker startup, incredible performance, no moving parts, less
heat, longer battery life, incredible reliability and durability
will soon enough conquer the obstacles of price, storage
restrictions and availability.
 In coming years SSD will replace Hard Disk Drives.

53. Thank You.
Questions ?

54. References
http://www.thessdreview.com
Shyam Jos, Blogger at FAQsPedia
Prof Hong Jiang – Department of CSE,University of Nebraska – Lincoln
http://www.notebookreview.com
http://computer.howstuffworks.com/
Dennis Martin ,Demartek
AnandTech.com