Filesystems · Cluster
Flash and Block Layers
FTL behavior, discard, and I/O schedulers.
- 01 Erase Blocks, Pages, and the Asymmetry That Shapes Flash Storage Why NAND programs a page once and erases a whole block, and how that mismatch forces every layer above the device to maintain a mapping and a collector.
- 02 Mapping Granularity in a Flash Translation Layer Page-level, block-level, and hybrid address mapping, the DRAM each one costs, and how a controller rebuilds its table from page spare areas after power loss.
- 03 Garbage Collection and Where Write Amplification Comes From Why reclaiming an erase block copies live pages, how the victim-selection policy sets the copy cost, and the closed-form relation between free space and amplification.
- 04 Wear Leveling and the Erase-Cycle Budget of a Flash Device How erase counts are tracked, what dynamic and static leveling each accomplish, and why the endurance rating is a property of the worst block rather than the average.
- 05 Discard and TRIM: Telling the Device Which Blocks Are Free How discard requests travel from the filesystem to the device, why they are advisory, what a secure erase adds, and the cost of queuing them badly.
- 06 Multi-Queue Block Dispatch and Why One Lock Was Not Enough The single-queue block layer, the contention that replaced it, and how software queues, hardware queues, and tags carry a request from submit to completion.
- 07 Choosing an I/O Scheduler and Setting Queue Depth What an elevator can still do on a device with no seek cost, the difference between the none, mq-deadline, and Kyber schedulers, and how queue depth controls latency.
- 08 Logical Block Size, Read-Modify-Write, and Misaligned I/O Why a device with 4 KiB pages can still accept 512-byte sectors, what that emulation costs internally, and how alignment and atomicity guarantees interact.
- 09 Cache Flush, FUA, and What a Write Completion Means How a device with a volatile write cache reorders writes, what a flush and a force-unit-access write each promise, and why the barrier is only as good as the drive.
- 10 Zoned Block Devices and the Zone Append Model How zone semantics replace the random-write abstraction with explicit sequential-write regions, what append buys, and which costs move from the device to the host.