ICNにおけるストリーミングコンテンツ配信のインネットワークキャッシング方式

早大学位記番号:新7734早稲田大

CRAID: Online RAID upgrades using dynamic hot data reorganization

Current algorithms used to upgrade RAID arrays typically require large amounts of data to be migrated, even those that move only the minimum amount of data required to keep a balanced data load. This paper presents CRAID, a self-optimizing RAID array that performs an online block reorganization of frequently used, long-term accessed data in order to reduce this migration even further. To achieve this objective, CRAID tracks frequently used, long-term data blocks and copies them to a dedicated partition spread across all the disks in the array. When new disks are added, CRAID only needs to extend this process to the new devices to redistribute this partition, thus greatly reducing the overhead of the upgrade process. In addition, the reorganized access patterns within this partition improve the array’s performance, amortizing the copy overhead and allowing CRAID to offer a performance competitive with traditional RAIDs. We describe CRAID’s motivation and design and we evaluate it by replaying seven real-world workloads including a file server, a web server and a user share. Our experiments show that CRAID can successfully detect hot data variations and begin using new disks as soon as they are added to the array. Also, the usage of a dedicated partition improves the sequentiality of relevant data access, which amortizes the cost of reorganizations. Finally, we prove that a full-HDD CRAID array with a small distributed partition (<1.28% per disk) can compete in performance with an ideally restriped RAID-5 and a hybrid RAID-5 with a small SSD cache.Peer ReviewedPostprint (published version

A Survey on the Integration of NAND Flash Storage in the Design of File Systems and the Host Storage Software Stack

With the ever-increasing amount of data generate in the world, estimated to reach over 200 Zettabytes by 2025, pressure on efficient data storage systems is intensifying. The shift from HDD to flash-based SSD provides one of the most fundamental shifts in storage technology, increasing performance capabilities significantly. However, flash storage comes with different characteristics than prior HDD storage technology. Therefore, storage software was unsuitable for leveraging the capabilities of flash storage. As a result, a plethora of storage applications have been design to better integrate with flash storage and align with flash characteristics. In this literature study we evaluate the effect the introduction of flash storage has had on the design of file systems, which providing one of the most essential mechanisms for managing persistent storage. We analyze the mechanisms for effectively managing flash storage, managing overheads of introduced design requirements, and leverage the capabilities of flash storage. Numerous methods have been adopted in file systems, however prominently revolve around similar design decisions, adhering to the flash hardware constrains, and limiting software intervention. Future design of storage software remains prominent with the constant growth in flash-based storage devices and interfaces, providing an increasing possibility to enhance flash integration in the host storage software stack

A Survey on the Integration of NAND Flash Storage in the Design of File Systems and the Host Storage Software Stack

With the ever-increasing amount of data generate in the world, estimated to reach over 200 Zettabytes by 2025, pressure on efficient data storage systems is intensifying. The shift from HDD to flash-based SSD provides one of the most fundamental shifts in storage technology, increasing performance capabilities significantly. However, flash storage comes with different characteristics than prior HDD storage technology. Therefore, storage software was unsuitable for leveraging the capabilities of flash storage. As a result, a plethora of storage applications have been design to better integrate with flash storage and align with flash characteristics. In this literature study we evaluate the effect the introduction of flash storage has had on the design of file systems, which providing one of the most essential mechanisms for managing persistent storage. We analyze the mechanisms for effectively managing flash storage, managing overheads of introduced design requirements, and leverage the capabilities of flash storage. Numerous methods have been adopted in file systems, however prominently revolve around similar design decisions, adhering to the flash hardware constrains, and limiting software intervention. Future design of storage software remains prominent with the constant growth in flash-based storage devices and interfaces, providing an increasing possibility to enhance flash integration in the host storage software stack

Enhancing Cache Robustness in Named Data Networks

Information-centric networks (ICNs) are a category of network architectures that focus on content, rather than hosts, to more effectively support the needs of today’s users. One major feature of such networks is in-network storage, which is realized by the presence of content storage routers throughout the network. These content storage routers cache popular content object chunks close to the consumers who request them in order to reduce latency for those end users and to decrease overall network congestion. Because of their prominence, network storage devices such as content storage routers will undoubtedly be major targets for malicious users. Two primary goals of attackers are to increase cache pollution and decrease hit rate by legitimate users. This would effectively reduce or eliminate the advantages of having in-network storage. Therefore, it is crucial to defend against these types of attacks. In this thesis, we study a specific ICN architecture called Named Data Networking (NDN) and simulate several attack scenarios on different network topologies to ascertain the effectiveness of different cache replacement algorithms, such as LRU and LFU (specifically, LFU-DA.) We apply our new per-face popularity with dynamic aging (PFP-DA) scheme to the content storage routers in the network and measure both cache pollution percentages as well as hit rate experienced by legitimate consumers. The current solutions in the literature that relate to reducing the effects of cache pollution largely focus on detection of attacker behavior. Since this behavior is very unpredictable, it is not guaranteed that any detection mechanisms will work well if the attackers employ smart attacks. Furthermore, current solutions do not consider the effects of a particularly aggressive attack against any single or small set of faces (interfaces.) Therefore, we have developed three related algorithms, namely PFP, PFP-DA, and Parameterized PFP-DA. PFP ensures that interests that ingress over any given face do not overwhelm the calculated popularity of a content object chunk. PFP normalizes the ranks on all faces and uses the collective contributions of these faces to determine the overall popularity, which in turn determines what content stays in the cache and what is evicted. PFP-DA adds recency to the original PFP algorithm and ensures that content object chunks do not remain in the cache longer than their true, current popularity dictates. Finally, we explore PFP-β, a parameterized version of PFP-DA, in which a β parameter is provided that causes the popularity calculations to take on Zipf-like characteristics, which in turn reduces the numeric distance between top rated items, and lower rated items, favoring items with multi-face contribution over those with single-face contributions and those with contributions over very few faces. We explore how the PFP-based schemes can reduce impact of contributions over any given face or small number of faces on an NDN content storage router. This in turn, reduces the impact that even some of the most aggressive attackers can have when they overwhelm one or a few faces, by normalizing the contributions across all contributing faces for a given content object chunk. During attack scenarios, we conclude that PFP-DA performs better than both LRU and LFU-DA in terms of resisting the effects of cache pollution and maintaining strong hit rates. We also demonstrate that PFP-DA performs better even when no attacks are being leveraged against the content store. This opens the door for further research both within and outside of ICN-based architectures as a means to enhance security and overall performance.Ph.D.College of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttps://deepblue.lib.umich.edu/bitstream/2027.42/145175/1/John Baugh Final Dissertation.pdfDescription of John Baugh Final Dissertation.pdf : Dissertatio

RAIDX: RAID EXTENDED FOR HETEROGENEOUS ARRAYS

The computer hard drive market has diversified with the establishment of solid state disks (SSDs) as an alternative to magnetic hard disks (HDDs). Each hard drive technology has its advantages: the SSDs are faster than HDDs but the HDDs are cheaper. Our goal is to construct a parallel storage system with HDDs and SSDs such that the parallel system is as fast as the SSDs. Achieving this goal is challenging since the slow HDDs store more data and become bottlenecks, while the SSDs remain idle. RAIDX is a parallel storage system designed for disks of different speeds, capacities and technologies. The RAIDX hardware consists of an array of disks; the RAIDX software consists of data structures and algorithms that allow the disks to be viewed as a single storage unit that has capacity equal to the sum of the capacities of its disks, failure rate lower than the failure rate of its individual disks, and speeds close to that of its faster disks. RAIDX achieves its performance goals with the aid of its novel parallel data organization technique that allows storage data to be moved on the fly without impacting the upper level file system. We show that storage data accesses satisfy the locality of reference principle, whereby only a small fraction of storage data are accessed frequently. RAIDX has a monitoring program that identifies frequently accessed blocks and a migration program that moves frequently accessed blocks to faster disks. The faster disks are caches that store the solo copy of frequently accessed data. Experimental evaluation has shown that a HDD+SSD RAIDX array is as fast as an all-SSD array when the workload shows locality of reference