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On-disk File Timestamps

The Single Unix Specification, Base Definitions (XBD), Section 4.8 entitled “File Times Update” states “An implementation may update timestamps that are marked for update immediately, or it may update such timestamps periodically.” This means that, for example, that file read and write operations are free to set the appropriate flags in the in-memory structures and do the actual updating of the on-disk filesystem structures at a later time. Assuming periodically means from time to time, it implies that a POSIX-compliant operating system is free to update it’s on-disk structures when it is convenient for the operating system to do so.

Samsung F2FS

Flash-Friendly File System (F2FS) is a Linux-based log-structured flash file system which takes into account the characteristics of NAND flash memory-based storage devices such as solid-state disks, eMMC, and SD cards with an built-in FTL (flash translation layer). It was developed and is maintained and enhanced by Samsung Electronics. Other available Linux flash file systems, such as jffs2, ubifs and logfs, are targeted at raw flash devices. f2fs was merged into the Linux 3.8 kernel. F2FS is based on Log-structured File System (LFS), which supports versatile “flash-friendly” features. The design has been focused on addressing the fundamental issues in LFS,