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The ext4, Btrfs, XFS, JFS, and F2FS file systems include support for the discard (TRIM or UNMAP) function. To make use of TRIM, a file system must be mounted using the discard parameter. Linux swap partitions are by default performing discard operations when the underlying drive supports TRIM, with the possibility to turn them off.
A solid-state drive (SSD) provides secondary storage for relatively complex systems including personal computers, embedded systems, portable devices, large servers and network-attached storage (NAS). To satisfy such a wide range of uses, SSDs are produced with various features, capacities, interfaces and physical sizes and layouts. [4]
bcache (abbreviated from block cache) is a cache mechanism in the Linux kernel's block layer, which is used for accessing secondary storage devices. It allows one or more fast storage devices, such as flash-based solid-state drives (SSDs), to act as a cache for one or more slower storage devices, such as hard disk drives (HDDs); this ...
Adding a new block somewhere else and indicating that F has a second extent; Moving files in the way of the expansion elsewhere, to allow F to remain contiguous; Moving file F so it can be one contiguous file of the new, larger size; The second option is probably impractical for performance reasons, as is the third when the file is very large.
The SSD controller will use free blocks on the SSD for garbage collection and wear leveling. The portion of the user capacity which is free from user data (either already TRIMed or never written in the first place) will look the same as over-provisioning space (until the user saves new data to the SSD).
Defragmentation is the operation of moving file extents (physical allocation blocks) so they eventually merge, preferably into one. Doing so usually requires at least two copy operations: one to move the blocks into some free scratch space on the disk so more movement can happen, and another to finally move the blocks into their intended place.
The number of defective blocks in different chips within a NAND flash memory varies: a given chip could have all its data blocks worn out while another chip in the same device could have all its blocks still active. Global wear leveling addresses this problem by managing all blocks from all chips in the flash memory together―in a single pool.
Contrary to (for example) an overwrite operation, a delete will not involve a physical write to the sectors that contain the data. Since a common SSD has no knowledge of the file system structures, including the list of unused blocks/sectors, the storage medium remains unaware that the blocks have become available.