Solid state drives


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  • Two main types of NAND flash have been used: single-level cell (SLC) and multi-level cell (MLC) flash. SLC flash stores one bit per cell, or memory location, within the NAND flash. MLC stores two bits per cell. SLC flash has higher read/write performance and greater write endurance, but MLC carries a lower cost per gigabyte because it offers approximately double the storage capacity in a similar amount of silicon. MLC flash is also made in higher volumes due to its application in consumer electronics and other devices, adding to its cost effectiveness. While SLC flash is common in enterprise server applications, virtually all SSDs used in client PCs and handheld devices today use MLC flash because of its cost advantage over SLC.
  • Processor - 16 or 32 bit embedded microcontroller, programmed in C in most cases, and compiled to run on the target CPU engine Error Correction (ECC) - A hardware function that appends redundancy bits with each byte stored in order to provide data error detection and correction upon readout.  Flash Controller - Contains the addressing, data bus, and control for managing one or more Flash components. A typical SSD controller will manage up to 512GB of Flash.  DRAM Controller - Contains the addressing, data bus, and control for managing one or more DRAM components. A typical SSD controller can manage up to 256MB of DRAM. I/O interface (i.e.: SATA) - Contains the native electrical interface per a particular open system standard such as SATA, USB, or SAS. The interface is controlled by the controller firmware driver.  Basic addressing and handshaking is done in hardware. Controller Memory - Comprised of programmed memory (ROM) and scratchpad/buffer RAM tightly coupled to the processor. This memory is used by the controller for program execution and for storing scratchpad values. In some cost constrained applications the RAM acts as the sole data buffer for the SSD. Chip Configuration - Establishes setting for types and speeds of memory parts used, clock inputs, diagnostic I/O, and LED status outputs. General I/O - General purpose programmable pins available to the application.  
  • Data Interface – usually 8 bit, sometimes 16 bit in denser parts I/O Controller – Multiplexes data, command, and status word types. Decodes commands Control Logic – Manages I/O transaction handshaking with Flash controller Address Register  – Identifies the block to be accessed for read or write Data/Cache register – a single word static register to buffer data between I/O and Array Status register – Flags errors in transactions and data flow Row/Column Decode – breaks Address value into page values Flash Array – the Flash cells arranged in rows and columns  
  • Serial Advanced Technology Attachment Interface   Description Details Standards SATA Serial ATA    A serial implementation of the Parallel ATA interface (also called the IDE) used on floppy drives and early magnetic disk drives. A point-to-point system that utilizes a 7-conductor cable with two differential [Tx/Rx] pairs to each drive. A separate 15-pin power connector is used.   Data throughput potential is 150, 300, or 600 Mbytes/s, based on the version used. The max unshielded cable length is 1 meter, 2 meters if shielded, or up to 8 meters using the xSATA version.  Serial ATA Revision 3.0, 5/2009 T13 committee --------------------------------------------------------------------------- FC Fibre Channel A multiple rate serial  Gbit, Multiprotocol interface.   Fibre Channel was developed as a modern serial interface for Storage Area Networks (SAN) where an array of drives in the same cabinet, room, or facility where shared by a set of servers. A bidirectional interface that supports SCSI, IP, ATM, HIPPI, and/or IEEE802.2 over copper or fiber optic cables. Rates from 1 to 10 Gbits/s based on version used.   Twister pair: 33 meters Coax: 75 meters Fiber Optic: 10 kilometers   In addition, FC can be configured in an arbitrated loop containing up to 127 devices, Point to Point,  or in a switched fabric.   SSD drives using Fibre channel support the twisted pair electrical interface and most use the 40-pin SCA-2 connector. This connector contains 4 twisted pairs for the base FC signals as well as various configuration, power, and ground pins. Maximum length 1 meter.   SSD drives utilize the Fibre Channel Protocol FCP-SCSI protocol command set. (SCSI - Small Computer System Interface). T10 committee ----------------------------------------------------------------------------------- SAS Serial Attached SCSI A 3 or 6-Gbit rate serial implementation of the 8/16/32-bit wide parallel Small Computer Systems Interface (SCSI) A point-to-point full duplex system. It utilizes a 4 two differential [Tx/Rx] pairs to each drive. A separate 15-pin power connector is used when combined with SATA, or can be integrated into a single connector. There are various connectors utilized.   Data throughput potential is 3 or 6 Gbits/s with 12 Gbits/s planned for 2012 release.     The max cable length is 10 meters.  Serial Attached SCSI - 2.0 {SAS-2.0), 11/2007 T10 committee -------------------------------------------------------------------------------------------- USB Universal Serial Bus A simple serial bus with integrated power.   Base data rate is 12 Mbits/s. Later versions support up to 480 Mbits/sec. A 4-pin bidirectional serial bus using a hub and spoke topology in order to connect up to 128 devices under the control of one master controller.   The current USD 2.0 standard allows operation 5 meters per cable but supports a string of cables with intermediate hubs to achieve a 30 meter maximum cable length.   SSD thumb drives and many form factor drives provide a USD interface as a secondary access channel. This is possible since the controller chip used in many form factor SSD drives only needs to use a few pins to integrate this interface into the drive design. USB 2.0 Specification
  • SSD vs. HDD 2.5” SATA 3.8Gbps SSD 2.5” SATA 3.8Gbps Solid NAND Flash HDD based Mechanism type Magnetic rotating platters 64GB Density 80GB 73g Weight 365g Read: 100MB/s Write: 80 MB/s Performance Read: 59MB/s Write: 60MB/s 1W Active Power Consumption 3.86W 1,500G/.5ms shock resistance 170G/.5ms 20G (10~2000Hz) Operating Vibration 0.5G (22~350Hz) 1500G for 0.5ms Shock Resistance 170G for 0.5ms 0 °C– 70°C Operating temperature 5°C– 55°C None Acoustic Noise 0.3 dB MTBF > 2M hours Endurance MTBF < 0.7M hours Source:
  • Solid state drives

    1. 1. SOLID STATE DRIVES Presented By: Manmath Agarwal IT-A 8th SEM
    2. 2. Contents•History • SSD Architecture•Solid State Drives • SSD Around us•NAND Flash Memory • Inter x25 SSD- an•SSD Elements Example 1. SSD Controller • Benefits of SSD 2. SSD Flash • SSD vs. HDD 3. SSD Interfaces • Application•SSD Storage Scheme
    3. 3. History• Storage Devices are evolved as the use of machines is increasing. Punch Cards (in 1940s). Magnetic Tapes/Drives (in 1950s). Hard Drives. Solid State Drives.
    4. 4. Solid State Drive(SSD)• SSD is an PC storage device that uses Solid State memory to store information.• SSD uses non volatile NAND Flash Memory , which enables it to retain data when the power is removed.
    5. 5. NAND Flash Memory• NAND Flash Memory is the key component of SSD.• It is a specific type of EEPROM chip.• It has a grid of columns and rows with a cell that has two transistors at each intersection as Control gate and Floating gate transistor.• The principle of operation is based on MOSFETs.
    6. 6. Types of NAND Flash• Single Level Cell (SLC)• Multi Level Cell (MLC)
    7. 7. SLC vs. MLC ITEM SLC MLCVoltage 3.3V/1.8V 3.3VChip Size 0.12um 0.16umPage Size/Block Size 2KB/128KB 512B/32KB or 2KB/256KBAccess Time(Max.) 25us 70usEndurance 100K 10KCost per Bit more Comparatively lessWrite Data Rate 8MB/s+ 1.5MB/s
    8. 8. SSD ElementsSSD consists of basically three elements:• SSD Controller.• SSD Flash.• SSD Interface.
    9. 9. SSD Controller• Flash controller includes the electronics that bridge the Flash memory components to the SSD input/output interfaces.• The controller is an embedded processor that executes firmware-level software.
    10. 10. SSD Controller Block Diagram• Processor• ECC• Flash Controller• DRAM Controller• I/O Interface• Controller Memory• Chip Configuration
    11. 11. SSD Flash• Solid State Flash memory is available using NAND technology.• NAND Flash components come in densities from 1Gb (gigabit) to 64Gb per chip.• NAND Flash components have structures called pages and blocks.• There is an Error Correction Code (ECC) associated with each sector.• NAND Flash has a limited rewrite endurance of about 1,000,000 times per block.
    12. 12. SSD Flash Block Diagram• Data Interface• I/O Controller• Control Logic• Address Register• Data/Cache register• Status register• Row/Column Decode• Flash Array
    13. 13. SSD Interface• Interface is used to connect the SSD with the computer.• Also, since SDDs are generally used in conjunction with magnetic disk drives, a common mass storage bus interface is used in most cases.• SSD are available with a variety of system interfaces based primarily on the performance requirements: Serial ATA Serial attached SCSI Fiber Channel USB
    14. 14. SSD Storage Scheme• Groups of NAND flash cells are organized into pages and these pages are organized into blocks.• Read and write operations can be performed on pages, but erase operations can only be performed at the block level.• This means that when rewriting a page, the entire block must be erased first.• The SSD controller manages this process.
    15. 15. • Page Size is
    16. 16. SSD Architecture
    17. 17. SSD Around Us Solid-State Disks (SSD) Mobile Media Players Embedded Thumb Disks Multimedia Systems Memory Cards
    18. 18. Intel x25 SSD- An Example• Certified for 25 MB/s read speed and 70 MB/s write speed.• MLS SSD standard.• 10-channel memory controller.• Each channel is “responsible” for two memory chips.• Storage/Intel-X25-M-SSD.html
    19. 19. Intel x25 SSD
    20. 20. Benefits of SSD• Faster start up of Solid State Drive• Faster access• Faster application launch time• More energy efficient• More reliable• More robust under extreme conditions• Lighter
    21. 21. SSD vs. HDD2.5” SATA 3.3 Gbps SSD 2.5” SATA 3.8 Gbps HDDSolid NAND Flash based Mechanism Type Magnetic Rotating platters64GB Density 80 GB75gm Weight 365gmRead: 100MB/s Performance Read: 59MB/sWrite: 80MB/s Write: 60MB/s1W Active Power Consumption 3.86W10-2000Hz Operating Vibration 22-350Hz1500G/0.5ms Shock Resistance 170G/).5ms0 °C– 70°C Operating Temperature 5°C– 55°CNone Acoustic Noise 0.3 dBMTBF > 2M hours Endurance MTBF < 0.7M hours
    22. 22. Application• SSDs were mainly used in those aspects of mission critical applications where the speed of the storage system needed to be as fast as possible.• Organizations that can benefit from faster access of system data include equity trading companies, telecommunication corporations, and video streaming.• SSD are used as cache at server side of Enterprises.
    23. 23. References••••
    24. 24. Thank You.
    25. 25. Queries ???
    26. 26. •SSD Architecture•SSD Around us•Inter x25 SSD- an Example•Benefits of SSD•SSD vs. HDD•Application