When data changes, it must be written again.

Unlike traditional hard drives, data on SSDs canвЂ™t be directly overwritten. Each block contains a specified number of pages (from 32 to 256), which contain a specified amount of data (2 to 8KB). What represents a challenge is that with an SSD you can write on a page any time, but you can erase only one block at a time. SSDs contain memory cells organized into pages and blocks.

Manufacturers address this issue with so-called wear leveling, which prevents SSD memory cells (the pages) from wearing out. Writing to an SSD is like writing on a piece of paper with a pencil: if you erase the same space too many times, it can wear out. There is one thing to note, though, and that is that there are a limited number of P/E cycles an SSD can support. Writing to an SSD is totally different than writing to a traditional hard drive: the SSD first clears existing information from the flash memory cells and programs new data into them hence, the writing process is often referred as program/erase cycles or P/E cycles. There is one tiny command line you must type into Terminal to enable a feature meant to expand the lifespan of the newly installed drive this feature is called TRIM. However, you shouldnвЂ™t stop at installing a new SSD. YouвЂ™ll notice the huge performance improvement right from the first time you boot up and immediately praise yourself for making this investment. The best way to expand your MacвЂ™s lifespan and obtain a significant speed boost is by replacing the hard drive with a solid state drive (SSD).

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