In this paper, we propose a multi-level
fault-tolerant storage cluster called MFTS, which provides flexible reliability
for a wide variety of applications. MFTS makes use of a reliability upper-bound
(i.e., Parameter r ) to guide the process of adjusting fault-tolerance levels,
i.e., i-erasure(s) and i 2 f1; 2; :::; rg. In particular, MFTS can map an
appropriate coding scheme to an application with individual reliability
requirements. MFTS is capable of partitioning multi-level reliable storage
using a virtual storage space, thereby adapting to any changing reliability
demands of applications. We present the implementation of the MFTS system,
which adopts an intersecting zigzag sets code (IZS code) rather than
replication or general-purpose erasure codes. Our MFTS has three salient
features: partial updates, fast reconstructions, and minimal overhead of
fault-tolerance level transitions. To quantify performance optimization in our
storage cluster, we compare IZS-enabled MFTS with two storage clusters equipped
with the Vandermonde- and Cauchy-Reed-Solomon codes. The experimental results
show that: 1) three schemes have comparable user-response-time performance in
both the operational and degraded modes; 2) MFTS outperforms the other two
alternatives by up to 26.1% in the offline reconstruction case; 3) MFTS speeds
up the online reconstruction by up to 23.7% over the other two schemes with
marginal increase in user response time.
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