How Can Wear Leveling Extend the Life of an SSD?

What is an SSD?

A Solid-State Drive (SSD) is one of the most popular, fast and energy efficient solutions for storing and sharing information. Flash controller and NAND flash memory are two things that make up an SSD. The primary goal of SSD is to provide high performance of reading and writing for random and sequential data requests.

Unlike the HDD, SSD has no moving parts. An ordinary HDD consists of spinning platters that have data read and written to from an actuator that holds magnetic heads. HDD writes as well as reads data magnetically. However, the magnetic properties coupled with the spinning platters can lead to mechanical failures. Unlike HDD, the solid-state drive writes and reads data to flash memory chips that are made of silicon. SSDs are made by way of stacking chips in a grid to get different densities. Thanks to FGT (floating gate transistors), Nand flash memory is non-volatile so it can hold data even if the power source is turned off or disconnected.

What are SSDs Used for?

In comparison with fixed disks, SSDs provide much faster storage as well as the other performance benefits. By offering lower latency than HDDs solid-state drives can perform heavy read and random workloads. Because of its low latency, SSDs can read data immediately as well as directly from a particular flash SSD cell location.

Functions of a modern SSD:

The advantages of SSDs in comparison with HDDs:

How Long Do SSDs Last?

Pay attention to the various types of SSD storage: Single-Level Cell (SLC), Multi-Level Cell (MLC) and Triple Level Cell (TLC). SLC saves one bit per storage cell, MLC – two bits per cell and TLC – three bits per cell.

The more data per cell saved, the higher the need for the wear level. Storage types can be linked to writing cycles. The  lifetime of Multi-Level Cell (MLC) is about 1,000 to 10,000 program/erase cycles. In comparison to ordinary HDDs, the mechanism of SSD does not degrade when only reading data. This means that when just reading data, the mechanics of SSD will not wear out. Thus, it depends on deleting as well as writing processes.

The average SSD lifespan depends on its storage cells. The more storage cells it has, the longer its lifespan. Having a vast storage space, the storage cells can serve much longer as they often do not require to be rewritten.

Thanks to wear leveling, SSD has made a big step towards more effectiveness, robustness, and reliability.

What Is Wear Leveling?

SSD is not able to reach its optimal lifespan without wear leveling to make sure that all the drive’s memory chips (store data in blocks) are used up before the first cell will be written again. It also means the larger the SSD’s capacity, the longer the lifespan.

Without wear leveling, your SSD can fail much sooner than you want. The reason is Single Level Cell (SLC) and Flash NAND cells of an SSD are rated at between 10,000 or 100,000 erase cycles, up to 1,000,000 program/erase cycles. Each of them performs a certain amount of write as well as read operations. Flash controller assigns logical addresses from the operating system to the physical addresses of the Flash memory. Every new write is read, erased, modified and rewritten to the first location. It means that storage spaces are frequently used and as a result, are worn out faster. In case a couple of blocks are at the end of their lifespan, your SSD may become inoperable, which will lead to data loss. Thanks to wear leveling, data is arranged so that its program / erase cycles are evenly distributed among all of the blocks in the device.

Dynamic VS Static Wear Leveling

Dynamic SSD wear leveling polls erased blocks and chooses the block which has the lowest erase count for the next write. The one disadvantage of dynamic SSD wear leveling is that in case the block holds the data that is not accessed it will never be removed to the other block. It limits the number of blocks that may undergo wear leveling.

The work of static wear leveling is mostly the same as the one of dynamic wear leveling. However, it guarantees that the static data blocks are moved when their block erase count is lower than a certain threshold. It may reduce write performance due to flash controller overhead. However, in comparison with dynamic wear leveling, static wear leveling is more efficient as it more effectively extends the lifespan of SSDs.

SSD is a storage device that is necessary to optimize. Wear leveling is the best solution to achieve this, as it is one of the most essential as well as efficient technologies to expand the lifetime of your SSD.