| I/O Intensive applications require high-performance storage systems. The performance of a storage system is greatly affected by the characteristics of storage devices and the storage interfaces connecting hosts and storage devices. The existing SCSI bus does not provide reliability and scalability that many applications need. Serial storage interfaces have emerged to meet such needs. Among them, Serial Storage Architecture (SSA), in particular, provides spatial reuse feature that allows each of the non-overlapped simultaneous transfers to utilize full link bandwidth without a switch device. This feature provides a great potential in scalability. However, how much such potential could be achieved in practice is not obvious. The design issues addressed include how to eliminate link bottleneck, how to eliminate bottleneck on disks, how to effectively use device sharing and file sharing, and how to maximize the benefits of spatial reuse. An analytical model is derived in this thesis to, provide a better understanding of spatial reuse.; It is a trend that more intelligence and processing capability are added on storage devices to improve the performance. Disk-based XOR RAID is an example. It utilizes the on-drive processor for exclusive-or (XOR) computations. It can reduce the amount of data traffic on storage channels or networks and eliminates the needs for a RAID controller. The first design issue of disk-based XOR RAID addressed in this thesis is how to prevent the system from entering into a state of deadlock. The deadlock problem is modeled in this thesis from both the parity allocation and command execution point of view. Two deadlock-free schemes are proposed. Another design issue of disk-based XOR RAID is raised by its command execution dependency among multiple disks. Such dependency creates additional requirements on disk buffer resource and additional command latency. The design issues discussed and addressed include how to reduce buffer occupancy, how to determine a proper size of buffer space, how to increase disk efficiency in disk-based XOR RAID, and how to enhance the disk-scheduling disciplines so that the disk efficiency can be maintained or even increased by reducing the buffer requirement. |
