What is Flash Memory? basic terms getting started what is wear leveling, what are the types of SSD, SLC, EMLC, MLC

1. LSI Channel Solutions
Nytro SSD Flash 101 – Key Terms
Kent Abendroth - LSI Channel Manager 425-417-5245 – May 2012

2. What is Flash Memory?
Solid state storage that is 100X to 1000X faster than hard drives yet
provides non-volatility.
Feature/Benefit Limitations Remedies
Applications needing • Higher $/GB than HDD • Wear leveling to
low latency and high • Program-erase cycles ensure uniform wear
IOPS. causes write wear and • Minimize writes
limits write endurance
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3. Types of Flash Memory
Technology Feature Limitations
SLC (single level cell) Highest program-erase 100K program-erase cycles
cycles 1 year data retention
MLC (multiple level cell) 2X capacity of SLC 3K program-erase cycles
1 year data retention
eMLC (enterprise MLC) High capacity and longer 30K program-erase cycles
write life 3 months data retention
Binary 01 00 10 00 01 10 10 01
Ascii H i
SLC: 1 bit /cell
MLC: 2 bits/cell
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4. Flash Writes
Writing may require several steps:
1. Moving existing data to provide space
2. Erasing previously written data
3. Writing new data
Feature Benefit Limitations
Over Provisioning - Supports high – until the reserved
reserving unreported memory write rates memory has been used
for immediate writes
Garbage Collection - partially Necessary to meet Garbage collection may
used blocks are combined to capacity limit write rates
free blocks for new data specifications
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5. Writing Flash – No Overwrite Capability
Binary Ascii
01001000 H
Erase 11111111
Write 01101001 i
Remaining writes: 2500 2499
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6. Garbage Collection
Before After
LSI Nytro Value:
Offloading garbage collection to LSI Flash controller ASICs less effect on applications.
SandForce performs foreground garbage collection for higher write endurance.
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7. Wear Leveling
Writes and erasures are evenly distributed across storage. All flash
blocks experience the same amount of wear.
Feature/Benefit Limitations Remedies
Maximum endurance Increases flash Use dedicated flash
enabled by ensuring management tasks management
level write wear
Nytro/SandForce Value
Offloading management to dedicated SandForce controllers has less
effect on applications. Advanced wear leveling algorithms further extend
flash endurance.
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8. Write Amplification
Each write from an application may require several flash writes which
lowers endurance. Goal is to have amplification equal to 1.
Nytro/SandForce Value
Using data compression allows application to be less than 1.
Write Cliff
A sudden drop in write performance due to running
out of reserved flash blocks
Nytro/SandForce Value
Foreground garbage collection mitigates a drop in
performance
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9. LSI Storage Legacy – Innovation and Leadership
Storage Systems
Servers Network
Attached
PC SAS Storage
Switch
Network Switch
Direct
Attached
LSI Silicon and Component Products
Storage RAID Storage SAN HDD
HBAs
Software Adapter Controllers Silicon Silicon
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