2016 32nd Symposium on Mass Storage Systems and Technologies (MSST)

The performance of HDFS is critical to big data software stacks and has been at the forefront of recent efforts from the industry and the open source community. A key problem is the lack of flexibility in how data replication is performed. To address this problem, this paper presents Pfimbi, the first alternative to HDFS that supports both synchronous and flow-controlled asynchronous data replicat... View full abstract»

We introduce manylogs, a simple and novel concept of logging that deploys many scattered logs on disk such that small random writes can be appended into any log near the current disk head position (e.g., the location of last large I/O). The benefit is two-fold: the small writes attain fast durability while the large I/Os still sustain large bandwidth. Manylogs also inspire a new principle: decoupl... View full abstract»

Object-based cloud storage has been widely adopted for their agility in deploying storage with a very low up-front cost. However, enterprises currently use them to store secondary data and not for expensive primary data. The driving reason is performance; most enterprises conclude that storing primary data in the cloud will not deliver the performance needed to serve typical workloads. Our analysi... View full abstract»

Journaling file systems have been widely used where data consistency must be assured. However, we observed that the overhead of journaling can cause up to 48.2% performance drop under certain kinds of workloads. On the other hand, the emerging high-performance, byte-addressable Non-volatile Memory (NVM) has the potential to minimize such overhead by being used as the journal device. The traditiona... View full abstract»

Modern applications have their own update protocols to remain failure consistency. However, these protocols are implemented without a comprehensive understanding of the persistence properties of the underlying file systems and typically optimized for disk-based storage. As a result, they are complex, error-prone, and exhibit disappointing performance on emerging fast non-volatile memories (NVMs) d... View full abstract»

The byte-addressable Non-Volatile Memory (NVM) offers fast, fine-grained access to persistent storage, and a large volume of recent researches are conducted on developing NVM-based in-memory file systems. However, existing approaches focus on low-overhead access to the memory and only guarantee the consistency between data and metadata. In this paper, we address the problem of maintaining consiste... View full abstract»

Deduplication has become essential in disk-based backup systems, but there have been few long-term studies of backup workloads. Most past studies either were of a small static snapshot or covered only a short period that was not representative of how a backup system evolves over time. For this paper, we collected 21 months of data from a shared user file system; 33 users and over 4,000 snapshots a... View full abstract»

During data deduplication, on-disk fingerprint lookups lead to high disk traffic, resulting in a bottleneck. In this paper, we propose a “lazy” data deduplication method which buffers incoming fingerprints and performs on-disk lookups in batches, aiming to reduce the disk bottleneck. In deduplication in general, prefetching is used to improve the cache hit rate by exploiting locality within the in... View full abstract»

The requirements of deduplication systems have changed in the last years. Early deduplication systems had to process dozens to hundreds of backup streams at the same time while today they are able to process hundreds to thousands of them. Traditional approaches rely on stream-locality, which supports parallelism, but which easily leads to many non-contiguous disk accesses, as each stream competes ... View full abstract»

In archival systems, storage media are often replaced much earlier than their expected service life in exchange for other benefits of new media, such as higher capacity, bandwidth, and I/O operations per second, or lower costs. In an era of decreasing media density growth rates, retiring media early by considering only short-term benefits while discarding potential long-term cost benefits could ha... View full abstract»

Solid-state drives (SSDs) have become promising storage components to serve large I/O demands in modern storage systems. Enterprise class (high-end) SSDs are faster and more resilient than client class (low-end) SSDs but they are expensive to be deployed in large scale storage systems. It is an attractive and practical alternative to exploit the high-end SSDs as a cache and low-end SSDs as main st... View full abstract»

Continuous technology scaling makes NAND flash cells much denser. As a result, NAND flash is becoming more prone to various interference errors. Due to the hardware circuit design mechanisms of NAND flash, retention errors have been recognized as the most dominant errors, which affect the data reliability and flash lifetime. Furthermore, after experiencing a large number of programm/erase (P/E) cy... View full abstract»

Garbage collection is known to have a profound impact on SSD performance as it strongly influences the write amplification. Another key value that impacts the write amplification is the amount of over-provisioning, which lowers the write amplification at the cost of reducing the user-visible storage capacity. Write amplification occurs as the valid pages that remain on a block selected by garbage ... View full abstract»

Write amplification is a critical factor that limits the stable performance of flash-based storage systems. To reduce write amplification, this paper presents a new technique that cooperatively manages data in flash storage and nonvolatile memory (NVM). Our scheme basically considers NVM as the cache of flash storage, but allows the original data in flash storage to be invalidated if there is a ca... View full abstract»

NAND flash memory has been widely used in storage systems by offering greater read/write performance and lower power consumption than mechanical hard drives. Recently, the tradeoff between endurance, write speed, and read speed has been exploited from many ways for I/O performance improvement, which also induce the read/write latency variation. In this paper, the latency variation is exploited in ... View full abstract»

Cloud storage has gained increasing popularity in the past few years. In cloud storage, data is stored in the service provider's data centers, and users access data via the network. For such a new storage model, our prior wisdom about conventional storage may not remain valid nor applicable to the emerging cloud storage. In this paper, we present a comprehensive study and attempt to gain insight i... View full abstract»

There are various methods to evaluate the performance of file systems through the replay of file system traces. Despite this diversity, little attention was given on comparing the alternatives, thus bringing some skepticism about the results attained using these methods. In this paper, to fill this understanding gap, we analyze two popular trace replay methods through the lens of metrology. This c... View full abstract»

Distributed object storage architectures have become the de facto standard for high-performance storage in big data, cloud, and HPC computing. Object storage deployments using commodity hardware to reduce costs often employ object replication as a method to achieve data resilience. Repairing object replicas after failure is a daunting task for systems with thousands of servers and billions of obje... View full abstract»

In the past few years, mobile devices quickly gained high popularity in our daily life. Designed for ultra-mobility, these small yet powerful devices are fundamentally distinct from traditional computer systems (e.g., PCs and servers) - from the internal hardware architecture and software stack, to application behaviors. Storage, the slowest component in the I/O stack, plays an important role in m... View full abstract»

With cloud assistance, a mobile application can offload its resource-demanding computation tasks to the cloud (public cloud, cloudlet, or personal cloud, etc). This leads to a scenario where computation tasks in the same application run concurrently on both the mobile device and the cloud. These tasks need to save, read, and write files on both the mobile device and the cloud. An important challen... View full abstract»

Mobile databases and key-value stores provide consistency and durability through write-ahead logging. The traditional logging scheme appends the log records to the end of the log file and flushes the records to durable storage using fsync(). Due to the large block size of the underlying file system and the Journaling of Journal anomaly, the logging latency becomes the main bottleneck of the mobile... View full abstract»