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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.
For SSD devices, Windows 7 disables ReadyBoost and automatic defragmentation. [207] Despite the initial statement by Steven Sinofsky before the release of Windows 7, [200] however, defragmentation is not disabled, even though its behavior on SSDs differs. [208] One reason is the low performance of Volume Shadow Copy Service on fragmented SSDs ...
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).
One such innovation, flash memory, is a non-volatile storage medium that can be electrically erased and reprogrammed. Solid-state storage typically uses the NAND type of flash memory, which can be accessed in chunks smaller than the entire capacity of the device.
Each file is using 10 blocks of space. (Here, the block size is unimportant.) The remainder of the disk space is one free block. Thus, additional files can be created and saved after the file E. If the file B is deleted, a second region of ten blocks of free space is created, and the disk becomes fragmented.
Using TRIM defeats this layer of plausible deniability as the all-zero (or all-one) blocks created easily indicate what blocks are used. [74] It has been argued disabling TRIM might be suspicious too. [75] The original version of the TRIM command has been defined as a non-queued command by the T13 subcommittee, and consequently can incur ...
Data damage can be caused when, for example, a file is written to a sector on the drive that has been damaged. This is the most common cause in a failing drive, meaning that data needs to be reconstructed to become readable. Corrupted documents can be recovered by several software methods or by manually reconstructing the document using a hex ...
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.