The storage testbed used in our experiments consists of a server and a client connected over an isolated Gigabit Ethernet LAN (see Figure 2). Our server is a dual processor machine with two 933 MHz Pentium-III processors, 256 KB L1 cache, 1 GB of main memory and an Intel 82540EM Gigabit Ethernet card. The server contains an Adaptec ServeRAID adapter card that is connected to a Dell PowerVault disk pack with fourteen SCSI disks; each disk is a 10,000 RPM Ultra-160 SCSI drive with 18 GB storage capacity. For the purpose of our experiments, we configure the storage subsystem as two identical RAID-5 arrays, each in a 4+p configuration (four data disks plus a parity disk). One array is used for our NFS experiments and the other for the iSCSI experiments. The client is a 1 GHz Pentium-III machine with 256KB L1 cache, 512 MB main memory, and an Intel 82540EM Gigabit Ethernet card.
Both machines run RedHat Linux 9. We use version 2.4.20 of the Linux kernel on the client for all our experiments. For the server, we use version 2.4.20 as the default kernel, except for the iSCSI server which requires kernel version 2.4.2 and the NFS version 4 server which requires 2.4.18. We use the default Linux implementation of NFS versions 2 and 3 for our experiments. For NFS version 4, which is yet to be fully supported in vanilla Linux, we use the University of Michigan implementation (release 2 for Linux 2.4).
For iSCSI, we employ the open-source SourceForge Linux iSCSI implementation as the client (version 3.3.0.1) and a commercial implementation as the iSCSI server. While we found several high-quality open-source iSCSI client implementations, we were unable to find a stable open-source iSCSI server implementation that was compatible with our hardware setup; consequently, we chose a commercial server implementation.
The default file system used in our experiments is ext3. The file system resides at the client for iSCSI and at the server for NFS (see Figure 2). We use TCP as the default transport protocol for both NFS and iSCSI, except for NFS v2 where UDP is the transport protocol.
