Kaladhar Voruganti

Policy-based validation of SAN configuration

Historically, storage has been directly connected to servers for fast local access and easy configuration. In recent years, storage area networks (SANs) have defined an alternative storage paradigm that allows storage to be shared among servers using fast interconnects. One of the key challenges of SAN management is the large number of configuration problems that are encountered in a typical SAN deployment. These configuration problems can be addressed by SAN management software. However, hard-coding the SAN configuration rules into the management software is not a viable option since it is not possible to easily modify or replace old configuration rules and specify new policies and guidelines. In this paper, we propose a novel policy-based SAN configuration validation system that can be used to specify, store, and evaluate configuration policies for SANs. We also introduce five new operators for collection policies that are useful for evaluating a wide variety of practical SAN configuration policies found in practice. The policy-based SAN configuration checking approach proposed in this paper is discussed within the context of device interoperability constraints. However, this approach is extensible as it can also be used to enforce performance, reliability, and security-related configuration constraints.

POTSHARDS—a secure, recoverable, long-term archival storage system

Users are storing ever-increasing amounts of information digitally, driven by many factors including government regulations and the publics desire to digitally record their personal histories. Unfortunately, many of the security mechanisms that modern systems rely upon, such as encryption, are poorly suited for storing data for indefinitely long periods of time; it is very difficult to manage keys and update cryptosystems to provide secrecy through encryption over periods of decades. Worse, an adversary who can compromise an archive need only wait for cryptanalysis techniques to catch up to the encryption algorithm used at the time of the compromise in order to obtain “secure” data. To address these concerns, we have developed POTSHARDS, an archival storage system that provides long-term security for data with very long lifetimes without using encryption. Secrecy is achieved by using unconditionally secure secret splitting and spreading the resulting shares across separately managed archives. Providing availability and data recovery in such a system can be difficult; thus, we use a new technique, approximate pointers, in conjunction with secure distributed RAID techniques to provide availability and reliability across independent archives. To validate our design, we developed a prototype POTSHARDS implementation. In addition to providing us with an experimental testbed, this prototype helped us to understand the design issues that must be addressed in order to maximize security.

An analysis of three gigabit networking protocols for storage area networks

SCSI protocol is the protocol of choice for block storage management. Different transport mechanisms such as parallel SCSI, Fibre Channel, iSCSI and Infiniband can be used to transfer SCSI protocol data. Distance and connectivity limitations are the key drawbacks of parallel SCSI. Therefore, Fibre Channel, Infiniband and iSCSI (SCSI over TCP) are competing to emerge as the dominant next generation SCSI transport mechanism. By analyzing the different components of a network protocol, this paper evaluates whether Fibre Channel, Infiniband and iSCSI are (a) suitable for gigabit wire speeds (b) scalable across thousands of interconnected devices and (c) satisfy the needs of storage environments and storage protocols.

Internet Protocol storage area networks

The sheer scale of the storage needs of most organizations makes block storage management an important system administration problem. Application servers, databases, and file systems rely on an efficient underlying block storage system. The storage area network paradigm is fast emerging as a desirable block storage solution, due to its performance, resource-sharing, and capacity-scaling benefits. This paper shows that the ubiquitous Internet Protocol (IP) network is technically well-suited to host a storage area network. The paper presents the storage protocol, management, and security building blocks that are necessary for making IP storage a reality. The paper then discusses performance issues that must be addressed in order to make IP storage area networks competitive with other storage area network technologies.

Security vs performance: tradeoffs using a trust framework

We present an architecture of a trust framework that can be used to intelligently tradeoff between security and performance in a SAN file system. The primary idea is to differentiate between various clients in the system based on their trustworthiness and provide them with differing levels of security and performance. Client trustworthiness reflects its expected behavior and is evaluated in an online fashion using a customizable trust model. We also describe the interface of the trust framework with an example block level security solution for an out-of-band virtualization based SAN file system (SAN FS). The proposed framework can be easily extended to provide differential treatment based on data sensitivity, using a configurable parameter of the trust model. This allows associating stringent security requirements for more sensitive data, while trading off security for better performance for less critical data, a situation regularly desired in an enterprise.

An Adaptive Data-Shipping Architecture for Client Caching Data Management Systems

Data-shipping is an important form of data distribution architecture where data objects are retrieved from the server, and are cached and operated upon at the client nodes. This architecture reduces network latency and increases resource utilization at the client. Object database management systems (ODBMS), file-systems, mobile data management systems, multi-tiered Web-server systems and hybrid query-shipping/data-shipping architectures all use some variant of the data-shipping. Despite a decade of research, there is still a lack of consensus amongst the proponents of ODBMSs as to the type of data shipping architectures and algorithms that should be used. The absence of both robust (with respect to performance) algorithms, and a comprehensive performance study comparing the competing algorithms are the key reasons for this lack of agreement. In this paper we address both of these problems. We first present an adaptive data-shipping architecture which utilizes adaptive data transfer, cache consistency and recovery algorithms to improve the robustness (with respect to performance) of a data-shipping ODBMS. We then present a comprehensive performance study which evaluates the competing client-server architectures and algorithms. The study verifies the robustness of the new adaptive data-shipping architecture, provides new insights into the performance of the different competing algorithms, and helps to overturn some existing notions about some of the algorithms.

BRAHMA: Planning Tool for Providing Storage Management as a Service

Storage management is becoming the largest component in the overall cost of storage ownership. Most organizations are trying to either consolidate their storage management operations or outsource them to a storage service provider (SSP) in order to contain the management costs. Currently, there do not exist any planning tools that help the clients and the SSPs in figuring out the best outsourcing option. In this paper we present a planning tool, Brahma, that specifically addresses the above mentioned problem, as Brahma is capable of providing solutions where the management tasks are split between the client and SSP at a finer granularity. Our tool is unique because: (a) in addition to hardware/software resources, it also takes human skill set as an input; (b) it takes planning time window as input because plans that are optimal for a given time period (e.g. a month) might not necessarily be the most optimum for a different time period (e.g. a year); (c) it can be used separately by both the client and the SSP to do their respective planning; (d) it allows the client and the SSP to propose alternative solutions if certain input service level agreements can be relaxed. We have implemented BRAHMA, and our experiment results show that there definitely are cost benefits that one can attain by having a tool with the above mentioned functional properties.

Logan: Automatic management for evolvable, large-scale, archival storage

Archival storage systems designed to preserve scientific data, business data, and consumer data must maintain and safeguard tens to hundreds of petabytes of data on tens of thousands of media for decades. Such systems are currently designed in the same way as higher-performance, shorter-term storage systems, which have a useful lifetime but must be replaced in their entirety via a ldquofork-liftrdquo upgrade. Thus, while existing solutions can provide good energy efficiency and relatively low cost, they do not adapt well to continuous improvements in technology, becoming less efficient relative to current technology as they age. In an archival storage environment, this paradigm implies an endless series of wholesale migrations and upgrades to remain efficient and up to date. Our approach, Logan, manages node addition, removal, and failure on a distributed network of intelligent storage appliances, allowing the system to gradually evolve as device technology advances. By automatically handling most of the common administration chores-integrating new devices into the system, managing groups of devices that work together to provide redundancy, and recovering from failed devices-Logan reduces management overhead and thus cost. Logan can also improve cost and space efficiency by identifying and decommissioning outdated devices, thus reducing space and power requirements for the archival storage system.

A hybrid access model for storage area networks

We present HSAN & a hybrid storage area network, which uses both in-band (like NFS (R. Sandberg et al., 1985)) and out-of-band visualization (like SAN FS (J. Menon et al., 2003)) access models. HSAN uses hybrid servers that can serve as both metadata and NAS servers to intelligently decide the access model per each request, based on the characteristics of requested data. This is in contrast to existing efforts that merely provide concurrent support for both models and do not exploit model appropriateness for requested data. The HSAN hybrid model is implemented using low overhead cache-admission and cache-replacement schemes and aims to improve overall response times for a wide variety of workloads. Preliminary analysis of the hybrid model indicates performance improvements over both models.