Search results for "Flash file system"
showing 4 items of 4 documents
FADaC
2019
Solid state drives (SSDs) implement a log-structured write pattern, where obsolete data remains stored on flash pages until the flash translation layer (FTL) erases them. erase() operations, however, cannot erase a single page, but target entire flash blocks. Since these victim blocks typically store a mix of valid and obsolete pages, FTLs have to copy the valid data to a new block before issuing an erase() operation. This process therefore increases the latencies of concurrent I/Os and reduces the lifetime of flash memory. Data classification schemes identify data pages with similar update frequencies and group them together. FTLs can use this grouping to design garbage collection strategi…
An Analysis of Flash Page Reuse With WOM Codes
2018
Flash memory is prevalent in modern servers and devices. Coupled with the scaling down of flash technology, the popularity of flash memory motivates the search for methods to increase flash reliability and lifetime. Erasures are the dominant cause of flash cell wear, but reducing them is challenging because flash is a write-once medium— memory cells must be erased prior to writing. An approach that has recently received considerable attention relies on write-once memory (WOM) codes, designed to accommodate additional writes on write-once media. However, the techniques proposed for reusing flash pages with WOM codes are limited in their scope. Many focus on the coding theory alone, whereas o…
Improving MLC flash performance and endurance with extended P/E cycles
2015
The traditional usage pattern for NAND flash memory is the program/erase (P/E) cycle: the flash pages that make a flash block are all programmed in order and then the whole flash block needs to be erased before the pages can be programmed again. The erase operations are slow, wear out the medium, and require costly garbage collection procedures. Reducing their number is therefore beneficial both in terms of performance and endurance. The physical structure of flash cells limits the number of opportunities to overcome the 1 to 1 ratio between programming and erasing pages: a bit storing a logical 0 cannot be reprogrammed to a logical 1 before the end of the P/E cycle. This paper presents a t…
Extending SSD lifetime in database applications with page overwrites
2013
Flash-based Solid State Disks (SSDs) have been a great success story over the last years and are widely used in embedded systems, servers, and laptops.One often overlooked ability of NAND flash is that flash pages can be overwritten in certain circumstances. This can be used to decrease wear out and increase performance.In this paper, we analyze the potential of overwrites for the most used data structure in database applications: the B-Tree. We show that with overwrites it is possible to significantly reduce flash wear out and increase overall performance.