2 research outputs found
Page-Differential Logging: An Efficient and DBMS-independent Approach for Storing Data into Flash Memory
Flash memory is widely used as the secondary storage in lightweight computing
devices due to its outstanding advantages over magnetic disks. Flash memory has
many access characteristics different from those of magnetic disks, and how to
take advantage of them is becoming an important research issue. There are two
existing approaches to storing data into flash memory: page-based and
log-based. The former has good performance for read operations, but poor
performance for write operations. In contrast, the latter has good performance
for write operations when updates are light, but poor performance for read
operations. In this paper, we propose a new method of storing data, called
page-differential logging, for flash-based storage systems that solves the
drawbacks of the two methods. The primary characteristics of our method are:
(1) writing only the difference (which we define as the page-differential)
between the original page in flash memory and the up-to-date page in memory;
(2) computing and writing the page-differential only once at the time the page
needs to be reflected into flash memory. The former contrasts with existing
page-based methods that write the whole page including both changed and
unchanged parts of data or from log-based ones that keep track of the history
of all the changes in a page. Our method allows existing disk-based DBMSs to be
reused as flash-based DBMSs just by modifying the flash memory driver, i.e., it
is DBMS-independent. Experimental results show that the proposed method
improves the I/O performance by 1.2 ~ 6.1 times over existing methods for the
TPC-C data of approximately 1 Gbytes.Comment: 37 page
SSDFS: Towards LFS Flash-Friendly File System without GC operation
Solid state drives have a number of interesting characteristics. However,
there are numerous file system and storage design issues for SSDs that impact
the performance and device endurance. Many flash-oriented and flash-friendly
file systems introduce significant write amplification issue and GC overhead
that results in shorter SSD lifetime and necessity to use the NAND flash
overprovisioning. SSDFS file system introduces several authentic concepts and
mechanisms: logical segment, logical extent, segment's PEBs pool,
Main/Diff/Journal areas in the PEB's log, Diff-On-Write approach, PEBs
migration scheme, hot/warm data self-migration, segment bitmap, hybrid b-tree,
shared dictionary b-tree, shared extents b-tree. Combination of all suggested
concepts are able: (1) manage write amplification in smart way, (2) decrease GC
overhead, (3) prolong SSD lifetime, and (4) provide predictable file system's
performance