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The I/O Paths Affine SAN Search (IPASS) algorithm is a root cause search algorithm developed in our lab, Although it has initially targeted Storage Area Networks (SANs), IPASS is a generic algorithm that can be used efficiently as a building block for performance management solutions for various application domains.
IPASS is a novel method for root cause analysis of performance problems focusing on SANs. The solution is applicable to the broader definition of a SAN; including, in addition to the fabric, the storage controllers and the storage servers it connects. For such SANs, we have developed an I/O Paths Affine SAN Search algorithm. The algorithm uses configuration information typically available in a SAN to construct I/O paths that connect between consumers and providers of storage resources in a SAN. When a performance problem is reported for a storage consumer in the SAN, IPASS uses the configuration and mapping information, on-line, to discover the I/O paths for this consumer. As the paths discovery advances, IPASS performs an informed search for the root cause of the problem. The underlying rationale of our approach is that if the performance problem registered at the storage consumer is indeed related to the SAN itself, the root causes of the problem are likely to be found on the relevant I/O paths within the SAN. We have evaluated the performance of IPASS analytically and empirically and compared it to known, informed, and uninformed search algorithms. Our simulations show that IPASS scales 7 to 10 times better than the reference algorithms.
The IPASS methods and algorithm are patented and published. The details of the paper are as follows:
- D. Breitgand, E. Henis, O. Shehory, and L. Yerushalmi. Root-cause analysis for SAN performance problems: an I/O path affine search approach. IM-2005, pages 251-264, Nice, France, May 2005.
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