Section 5.7 Solid State Drives
In this section we discuss Solid State Drives chapter 44. Start by reading sections 44.1, 44.2.
Key take-away: SSD space is organized in blocks that contain pages. In order to write to a page within a block we must first erase the whole block.
Read section 44.3. Key takeaways:
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A read of a page happens fast, within microseconds, and from any location.
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An erase operation clears an entire block to prepare for writes to that block. It is expensive, taking milliseconds.
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A program operation writes to a page in a block that has been erased. Speed inbetween a read and an erase.
Thus pages can be in any of the following states:
INVALID (its block not erased yet), ERASED (can be written to) and VALID (can be read from).Read section 44.4. Key takeaway: flash drives wear out: Each block can be erased and reprogrammed at most around 10,000 times (MLC) or 100,000 times (SLC).
Read section 44.5, about the basics of turning the flash chip mechanism to a fully usable SSD drive. In particular the use of a flash translation layer (FTL)
Read sections 44.6 and 44.7 about the basic mechanisms for organizing SSDs, in particular about the advantages of a log-structured approach.
Skim through sections 44.8-44.10.
Read section 44.11 about SSD performance and cost, in particular the considerably faster random operations on an SSD compared to a HDD.
Read the summary on page 44.12.
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