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http:// thessdreview.com/

The hard disk drive (HDD) market is set to shrink from $37 billion in 2012 to $33 billion in 2013 and $32 billion in 2014 . ( http://www.nasdaq.com) Global shipments of solid-state drives are expected to more than double this year…

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http:// thessdreview.com/

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  1. The hard disk drive (HDD) market is set to shrink from $37 billion in 2012 to $33 billion in 2013 and $32 billion in 2014 . (http://www.nasdaq.com) • Global shipments of solid-state drives are expected to more than double this year… • Longer term, shipments are projected to reach 239 million units in 2016, comprising about 40% of the size of the market for hard-disk drives. http://thessdreview.com/

  2. same formfactor -size and shape to fit platter - not much to see actually

  3. Advantages • No spin-up time • Extremely low random access time (about 0.1ms) • Consistent read time throughout the SSD (while on a HDD if the data is written in a fragmented way, read ops will have varying response times) • Zero defragmentation • No noise (great for a home NAS) • Very light (SSDs size is 2,5" with SATA connectors) • Lower power consumption (Excellent for the environment ) • Unaffected by magnetic fields • Very robust

  4. Disadvantages • Cost per GB • Limited maximum capacity • Limited P/E cycles • Performance degradation • Write amplification (Garbage collection, trim) • Security issues (safe erase, cryptography)

  5. SSD components: Memory - Static RAM (SRAM battery powered) fastest (cache) - Dynamic RAM (DRAM battery powered) fast main ram - EEPROM (cancellazione totale) - Flash NOR (gates) NOR allows random-access for reading, Byte-Level access, slow replaces ROM, BIOS, Firmware - Flash NAND (gates) page/block access, cheap, fast SSD componetnts: Controller The controller is an embedded processor that executes firmware-level code and is one of the most important factors of SSD performance. Some of the functions performed by the controller include: Error correction (ECC) Wear leveling Bad block mapping Read scrubbing and read disturb management Read and write caching Garbage collection Encryption

  6. Disadvantages: wite amplification PHYSICAL BLOCKS CONTROLLER Applcation file Create, update, ... O.S. Filesystem

  7. Writing is possible only to empty cells, no overwriting • Writing is done at page level (4KB), erasing only at block level (128 pages = 512 KB)

  8. Disadvantages, W.A.: • Garbage collection • GC is the name for the process of relocating existing data to new locations and allowing the surrounding invalid data to be erased. • TRIM (O.S.) • The TRIM command is designed to enable the operating system to notify the SSD of which pages of data are • now invalid due to erases by the user or operating system itself. During a delete operation the OS will not only • mark the sectors as free for new data, but it will also send a TRIM command to the SSD with the associated • LBAs to be marked as no longer valid. After that point the SSD knows not to relocate the data from those LBAs • during garbage collection. • Wear Leveling limited P/E cycles • Moving the data around to make sure each cell is evenly worn.

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