Flash fundamentals

By the end of this course you should be able to:

- Explain flash storage technologies in the marketplace- Describe how flash storage is different from hard disks- List flash storage components- Define essential flash storage characteristics- Explain why NetApp is a leader in the flash storage marketplace

Flash-Accelerated storage

Flash devices

Enterprise Flash Storage components

Flash storage venders add value

Comparing SSDs to Hard disks

Flash page write, block erase:

The flash medium is divided into:

- Pages, which range in size form 512 bytes to 8 kilobytes and- Erase units, which consist of 32 to 128 contiguous pages and are frequently called “erase

blocks.”

Erase process:

1. Active erase block pages are copied out to a buffer.2. The erase block is flash erased.3. The buffer contents are written back with previous data and new data to any eligible erase

block.

Maintaining valid data in erase block.

Solid state technologies

Most use NAND technology. Early chips used NOR technology. Currently, flash is the predominate solid state storage technology.

Possible future solid state technologies are:

- Stacking memory- Phase change memory- Resistive RAM- Ferroelectric RAM

Endurance represents the amount of data you can write to a flash device during its lifetime, it is characterized by:

- Program/erase (P/E) cycles- Total bytes written (TBW)- Drive writes per day (DWPD)

Endurance early issues

High endurance flash:

- Was possible with SLC NAND technology- Was cost prohibitive

Lower cost flash

- Was possible with MLC NAND technology- Requires wear levelling techniques

Overprovisioning

- Provided extra capacity- Solved earlier endurance problems

Three classifications of endurance

1. Write-intensive = 25+DWPD2. Medium endurance = 10 DWPD3. Read-intensive = 1 to 3 DWPD

Flash media vendors use a combination of NAND type, overprovisioning, and software to reach a desired endurance level.

Flash media wear-life challenge

- Rewriting valid data from an erase block candidate amplifies writes- Write amplification increase wear- Wear is measured in P/E cycles, TBW, or DWPD.- Write-optimized software increases flash endurance.

Questions

1. Match each flash parameter to its correct definitiona. Write amplification

i. Characteristic of flash memory, where a single write on the host results in multiple writes to the flash medium over time

b. Garbage collectioni. Identifies block erase candidates through monitoring page active and

inactive states and monitoring cold data pages.c. Wear-Levelling

i. Evenly distributes page write and block erase operations over the flash memory chips in a device

d. Flash transition layeri. Presents the flash device to the host OS as a logical block device

2. What are the three major components of enterprise flash devices? (Choose three.)a. Flash memory (Correct)b. FAPIc. DRAM (Correct)d. Flash deregulatore. Flash controller (Correct)

3. How is flash storage wear life measured? (Choose three.)a. Total bytes written –TBW (Correct)b. Drive writes per day –DWPD (Correct)c. Flash endurance cycles -FECd. Program/Erase (P/E) cycles (Correct)e. Center to Edge (CTE)

4. What are two functions of the flash translation layer? (Choose two.)a. Defining the write cliffb. Supporting high availabilityc. Managing component wear (Correct)d. Mapping pages to logical blocks (Correct)e. Mirroring writes to alternate controller

http://www.netapp.com/us/media/flash-storage-for-dummies.pdf