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StarWind iSCSI SAN for Microsoft Windows: Best Practices Guide

INTRODUCTION
StarWind Windows-based iSCSI SAN software is designed specifically for the Windows 2003/Vista/2008/2008 R2 platforms and enables IT departments to extend Windows storage capabilities to provide cost effective network storage solutions. It supports all Windows ertified storage devices and hardware suchas Fibre Channel, SCSI, IDE and SATA. StarWind’s ability to work well with any hardware components makes the software extremely flexible. End users can configure StarWind using hardware that meets the minimum system requirements, or it can be installed on even the fastest hardware available on the market. Given the wide range of possible hardware configurations, this document provides guidelineson how to setup a StarWind server for optimal performance and availability.

via the pagefile. If StarWind has to wait for its data to be read from disk, this will result in increased latency which will result in lower I/O rates. StarWind leverages advanced I/O features and multi-thread capabilities available on the Windows platform which allows it to use the processor and memory sparingly. As arule of thumb, one iSCSI session typically consumes about 10 MB of memory. For optimal performance, StarWind Software recommends configuring the server to use a Xeon 2.8 GHz CPU with 512 MB of RAM.

Network Speed
iSCSI allows storage commands to be transmitted over a TCP/ IP network. TCP/IP is the virtual “wire” between a hard disk and a hard disk controller. Performance of TCP/IP can bemeasured in two ways: throughput and latency. Throughput is the amount of data transferred in a time period, usually defined in bytes per second. Latency is defined as the amount of time between the request of the data, and when the data becomes available, usually defined in milliseconds. In this case iSCSI is the communication medium between the initiators and StarWind Disks. In order to gain themaximum performance from the disk, the overhead of the network “wire” (latency) needs to be negligible while the transfer rate (throughput) is high. As such, optimal iSCSI performance is obtained by using a Gigabit or 10 GB network. A Gigabit or 10 GB network has low latency while providing maximum throughput. Gigabit Ethernet latency is typically less than the seek time of today’s hard drives, whileGigabit Ethernet throughput (1,000Mbps or 130MBps) is more than adequate for most existing drive technology.

CONFIGURING FOR PERFOMANCE Operating System
Taking full advantage of StarWind’s capabilities starts with the operating system. StarWind Software recommends a server class network operating system such as Windows 2003 Server, Windows Server 2008 or Windows Server 2008 R2. A serveroperating system is preferred for two reasons: first, a server operating system is optimized for a multi-user environment. One aspect of this optimization is the smaller CPU time slice or quantum granted to each process. Since StarWind typically handles multiple initiators concurrently, the smaller quantum means that requests are handled quicker resulting in lower latency. Secondly, the operating systemgives priority to a service over a foreground application. StarWind directly benefits from this because its core runs as a Windows service. Having higher priority over foreground applications ensures that StarWind gets as much processing time as it needs.

Processor And Physical Memory
The system processor plays an important role in StarWind’s performance. Unlike many hardware implementationsof iSCSI targets, StarWind relies on the host CPU to process all iSCSI requests. A slow processor delays StarWind from servicing incoming requests in a timely manner. If the processor is not fast enough to handle incoming packets, as the traffic increases the number of packets waiting to be processed continue to grow. This bottleneck not only drastically reduces performance but also causes...