An efficient model for dimensioning an ATA-based virtual storage system q Tien Van Do a,⇑ , Hyotaek Lim b , Ram Chakka c a Department of Telecommunications, Budapest University of Technology and Economics, H-1117, Magyar tudósok körútja 2, Budapest, Hungary b Department of Ubiquitous IT, Graduate School of Design and IT, Dongseo University, Sasang-gu, Busan 617-716, South Korea c Meerut Institute of Engineering and Technology (MIET), Meerut 250005, India article info Article history: Received 6 June 2011 Received in revised form 3 April 2012 Accepted 3 April 2012 Available online 8 May 2012 abstract Internet Advanced Technology Attachment (iATA) is a block-level storage network protocol used by iATA servers to offer a storage solution for clients. With iATA, mobile users can access their valuable data through the network from anywhere and at anytime as if the storage device is attached locally. In the iATA architecture, iATA servers and iATA clients exchange necessary protocol messages over IP networks. This paper proposes an analytical queuing model based on quasi-birth-and-death (QBD) processes to evaluate the performability of an iATA server in a network environment. An exact solution method is developed and presented, however it has state space explosion problem. Therefore, we present a novel computational algorithm to approximate the per- formance measures. Comparison with numerical results obtained by the exact solution shows that the proposed algorithm is both accurate and fast. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Storage limitations in mobile appliances have become a significant problem of research interest due to the rapid growth of data centric applications over IP. Block-level I/O protocols are preferred over file-level I/O protocols from the aspects of low latency, high performance and low overheads. Internet Small Computer System Interface (iSCSI) are a popular block- level I/O protocols that are deployed in Storage Area Networks (SAN) [1–6]. iSCSI protocols were developed by the Internet Engineering Task Force (IETF) to transport Small Computer System Interface (SCSI) commands, status, data over networks using the TCP/IP protocol [1–6]. Advanced Technology Attachment (ATA) provides a hard disk interface for storage solutions in the Small Office and Home Office (SoHo) environment due to its low cost and technological simplicity. ATA over Ethernet (AoE) is another well known storage interface, however this can be used only to access disks in local area network environments based on Ethernet. There have been some successful attempts to enable block-level ATA commands to be sent over the Internet. Towards the above, a new block-level storage network protocol, iATA (Internet Advanced Technology Attachment) has been proposed as a transport protocol for carrying ATA block-level access protocol over the ubiquitous TCP/IP network. With iATA, mobile users can access their valuable data through the network from anywhere and at anytime as if the storage device is attached locally [1–6]. The design of iATA and the proof of concept (the iATA server) were dealt in detail in [1–6]. Recently, there are several further contributions [7,8] that emphasize the importance and utility of the application of iATA for mobile users. To the knowledge of the authors, there have not been any analytical models with computational algorithms for the performance of iATA operation. Therefore, there is a need to derive a model and viable computational algorithms to evaluate the 0045-7906/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compeleceng.2012.04.002 q Reviews processed and proposed for publication to Editor-in-Chief by Associate Editor Dr. Yixin Diao. ⇑ Corresponding author. E-mail addresses: do@hit.bme.hu (T.V. Do), ramchakka@yahoo.com (R. Chakka). Computers and Electrical Engineering 38 (2012) 1388–1398 Contents lists available at SciVerse ScienceDirect Computers and Electrical Engineering journal homepage: www.elsevier.com/locate/compeleceng