System Software for Flash Memory: A Survey

Chung, Tae-Sun; Park, Dongjoo; Park, Sang Won; Lee, Dong‐Ho; Lee, Sang‐Won; Song, Ha-Joo

doi:10.1007/11802167_41

Cited by 91 publications

(48 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In order to maintain a small mapping table while achieving reasonable write performance, many FTLs [12,22,26,30] adopt a large mapping granularity (e.g. a block) and use one or multiple log blocks to hold data for incoming writes.…”

Section: Would Increasing Workload Randomness Degrade Performance?mentioning

confidence: 99%

Understanding intrinsic characteristics and system implications of flash memory based solid state drives

Chen

Koufaty

Zhang

2009

Proceedings of the Eleventh International Joint Conference on Measurement and Modeling of Computer Systems

348

161

View full text Add to dashboard Cite

Flash Memory based Solid State Drive (SSD) has been called a "pivotal technology" that could revolutionize data storage systems. Since SSD shares a common interface with the traditional hard disk drive (HDD), both physically and logically, an effective integration of SSD into the storage hierarchy is very important. However, details of SSD hardware implementations tend to be hidden behind such narrow interfaces. In fact, since sophisticated algorithms are usually, of necessity, adopted in SSD controller firmware, more complex performance dynamics are to be expected in SSD than in HDD systems. Most existing literature or product specifications on SSD just provide high-level descriptions and standard performance data, such as bandwidth and latency.In order to gain insight into the unique performance characteristics of SSD, we have conducted intensive experiments and measurements on different types of state-of-the-art SSDs, from low-end to high-end products. We have observed several unexpected performance issues and uncertain behavior of SSDs, which have not been reported in the literature. For example, we found that fragmentation could seriously impact performance -by a factor of over 14 times on a recently announced SSD. Moreover, contrary to the common belief that accesses to SSD are uncorrelated with access patterns, we found a strong correlation between performance and the randomness of data accesses, for both reads and writes. In the worst case, average latency could increase by a factor of 89 and bandwidth could drop to only 0.025MB/sec. Our study reveals several unanticipated aspects in the performance dynamics of SSD technology that must be addressed by system designers and data-intensive application users in order to effectively place it in the storage hierarchy.

show abstract

Section: Would Increasing Workload Randomness Degrade Performance?mentioning

confidence: 99%

Understanding intrinsic characteristics and system implications of flash memory based solid state drives

Chen

Koufaty

Zhang

2009

Proceedings of the Eleventh International Joint Conference on Measurement and Modeling of Computer Systems

348

161

View full text Add to dashboard Cite

show abstract

“…FTLs can be implemented at different granularities in terms of the size of a single entry capturing and address space in the mapping table. Many FTL schemes [8], [24], [19], [25] and their improvement by write-buffering [20] have been studied. A recent page-based FTL scheme called DFTL [11] utilizes temporal locality in workloads to overcome the shortcomings of the regular page-based scheme by storing only a subset of mappings (those likely to be accessed) on the limited SRAM and storing the remainder on the flash device itself.…”

Section: Introductionmentioning

confidence: 99%

A semi-preemptive garbage collector for solid state drives

Lee

Kim

Shipman

et al. 2011

(Ieee Ispass) Ieee International Symposium on Performance Analysis of Systems and Software

View full text Add to dashboard Cite

Abstract-NAND flash memory is a preferred storage media for various platforms ranging from embedded systems to enterprise-scale systems. Flash devices do not have any mechanical moving parts and provide low-latency access. They also require less power compared to rotating media. Unlike hard disks, flash devices use out-of-update operations and they require a garbage collection (GC) process to reclaim invalid pages to create free blocks. This GC process is a major cause of performance degradation when running concurrently with other I/O operations as internal bandwidth is consumed to reclaim these invalid pages. The invocation of the GC process is generally governed by a low watermark on free blocks and other internal device metrics that different workloads meet at different intervals. This results in I/O performance that is highly dependent on workload characteristics. In this paper, we examine the GC process and propose a semi-preemptive GC scheme that can preempt on-going GC processing and service pending I/O requests in the queue. Moreover, we further enhance flash performance by pipelining internal GC operations and merge them with pending I/O requests whenever possible. Our experimental evaluation of this semi-preemptive GC sheme with realistic workloads demonstrate both improved performance and reduced performance variability. Write-dominant workloads show up to a 66.56% improvement in average response time with a 83.30% reduced variance in response time compared to the non-preemptive GC scheme.

show abstract

“…There has been a host of techniques on improving the performance of the flash translation layer (FTL), which is the part of the flash controller that provides logical-to-physical address mapping, power-off recovery, and wear-leveling. Researchers have studied the FTL algorithms [3] and proposed various improvements on their performance based on block-level associativity [15], onchip caching [1], page-level lazy updates [18], or wear-leveling [11]. On the software side, research has focused on flash-specific bufferpool management schemes [14,16,20,21], query evaluation techniques [7,19,23], and logging [8].…”

Section: Related Workmentioning

confidence: 99%

Write-limited sorts and joins for persistent memory

Viglas

2014

Proc. VLDB Endow.

View full text Add to dashboard Cite

To mitigate the impact of the widening gap between the memory needs of CPUs and what standard memory technology can deliver, system architects have introduced a new class of memory technology termed persistent memory. Persistent memory is byteaddressable, but exhibits asymmetric I/O: writes are typically one order of magnitude more expensive than reads. Byte addressability combined with I/O asymmetry render the performance profile of persistent memory unique. Thus, it becomes imperative to find new ways to seamlessly incorporate it into database systems. We do so in the context of query processing. We focus on the fundamental operations of sort and join processing. We introduce the notion of write-limited algorithms that effectively minimize the I/O cost. We give a high-level API that enables the system to dynamically optimize the workflow of the algorithms; or, alternatively, allows the developer to tune the write profile of the algorithms. We present four different techniques to incorporate persistent memory into the database processing stack in light of this API. We have implemented and extensively evaluated all our proposals. Our results show that the algorithms deliver on their promise of I/O-minimality and tunable performance. We showcase the merits and deficiencies of each implementation technique, thus taking a solid first step towards incorporating persistent memory into query processing.

show abstract

System Software for Flash Memory: A Survey

Cited by 91 publications

References 5 publications

Understanding intrinsic characteristics and system implications of flash memory based solid state drives

Understanding intrinsic characteristics and system implications of flash memory based solid state drives

A semi-preemptive garbage collector for solid state drives

Write-limited sorts and joins for persistent memory

Contact Info

Product

Resources

About