Takayuki Fukatani

Adapting Storage Protocol Stack Using Custom File Metadata to Commodity Linux Servers

It has been a challenge for storage vendors to adapt their proprietary protocol stacks to commodity servers. Despite large development effort, many proprietary protocol stacks are available only on the specialized storage appliances because of the dependency on the hardware or software modules. Most of these protocol stacks use original filesystems to store custom file metadata to be compliant with the protocol specifications. In this paper, we propose the protocol metadata module (PMM) which enables the capability of the custom file metadata on Linux filesystems. PMM allows the protocol stacks using the custom file metadata to offer the protocol functions in a protocol compliant manner on Linux servers. We applied PMM to our proprietary protocol stack to confirm that PMM can achieve higher protocol function coverage and reasonable performance. Our evaluations show that PMM increases the protocol function coverage from 75.0% to 96.7% on Linux servers while suppressing the access performance degradation to at most 8% in the typical file server workloads.

A Method for Eliminating Metadata Cache Deallocation Latency in Enterprise File Servers

This paper presents an analysis of a performance bottleneck in enterprise file servers using Linux and proposes a modification to this operation system for avoiding the bottleneck. The analysis shows that metadata cache deallocation of current Linux causes large latency in file-request processing when the operational throughput of a file server becomes large. To eliminate the latency caused by metadata cache deallocation, a new method, called “split reclaim,” which divides metadata cache deallocation from conventional cache deallocation, is proposed. It is experimentally shown that the split-reclaim method reduces the worst response time by more than 95% and achieves three times higher throughput under a metadata-intensive workload. The split-reclaim method also reduces latency caused by cache deallocation under a general file-server workload by more than 99%. These results indicate that the split-reclaim method can eliminate metadata cache deallocation latency and make possible the use of commodity servers as enterprise file servers.