In modern I/O architectures, multiple disk drives are attached to each I/O bus. Under I/O-intensive workloads, the disk latency for a request can be overlapped with the disk latency and data transfers of requests to other disks, potentially resulting in an aggregate I/O throughput at nearly bus bandwidth. This paper reports on a performance impairment that results from a previously unknown form of convoy behavior in disk I/O, which we call rounds. In rounds, independent requests to distinct disks convoy, so that each disk services one request before any disk services its next request. We analyze log files to describe read performance of multiple Seagate Wren-7 disks that share a SCSI bus under a heavy workload, demonstrating the rounds behavior and quantifying its performance impact.
|Number of pages||9|
|State||Published - 1999|
|Event||Proceedings of the 1999 6th Workshop on I/O in Parallel and Disbributed Systems, IOPADS '99 (The ACM Federated Computing Research Conference, FCRC'99) - Atlanta, GA, USA|
Duration: 5 May 1999 → 5 May 1999
|Conference||Proceedings of the 1999 6th Workshop on I/O in Parallel and Disbributed Systems, IOPADS '99 (The ACM Federated Computing Research Conference, FCRC'99)|
|City||Atlanta, GA, USA|
|Period||5/05/99 → 5/05/99|