It may have taken a while for compliant products to materialise but the iSCSI protocol looks an interesting alternative to Fibre-Channel SANs. No need to implement expensive fibre cabling as iSCSI can use your existing infrastructure, including switches, as it is designed to transport SCSI data blocks across standard IP networks.
Overland Storage claims to be the first vendor to market and its new REO family consists of three disk appliance products. These aim to accelerate data backup and restore processes and are designed to sit between your application and backup servers, or between the tape device and backup servers. They are used to back up data directly to their hard disks simultaneously from multiple servers, which can then be accessed by the backup server and secured to tape more efficiently. Both the R2000 and RA2000 provide eight hard disks, so up to eight servers can be backed up at the same time and if further storage is required the RX2000 provides easy expansion options in 2TB increments.
The RA2000 is a well-built machine. Underneath the lid you’ll find a Tyan S2721 motherboard equipped with a pair of 2.4GHz Xeon processors, plus 512MB of PC2100 memory, running a Red Hat Linux kernel. Storage is handled by lower-cost Serial ATA (SATA) drives with eight 250GB WD2500 drives supplied in removable carriers. These are looked after by a 3Ware Escalade eight-port SATA controller, although hardware RAID is not an option and the drives are left configured as a JBOD (just a bunch of disks) array. However, once multiple drives have been associated with an iSCSI initiator you can create software-based RAID-0, -1 or -5 arrays on your servers. A 10/100BaseTX port to the left of the front panel is used for management access whilst a pair of 1000BaseT ports to the right provides access to data.
Installation is reasonably straightforward but the documentation could be better. At the very least, it should point out that the management port and two data ports must be on different subnets otherwise a conflict will occur stopping the data ports functioning correctly. All REO appliances use a USB drive installed in the port at the rear which provides configuration details specifically for that appliance. The web browser management interface is a simple affair with menu options for accessing the appliance’s network settings, monitoring its status and rebooting the unit. Once the data ports have been supplied with static IP addresses you can move on to storage configuration where you can create and apply iSCSI initiator names to each installed drive.
Overland also includes IBM’s software iSCSI initiator on the USB drive but we opted to download the latest Microsoft version which was easy enough to install on our Windows Server 2003 and 2000 Server systems.
Once the iSCSI initiators have been logged in to the targets the drives appear to the servers as another storage resource with a local drive letter – just as a fibre channel storage device does. For testing we created four iSCSI targets and associated them with a dual Xeon 2.4GHz Windows Server 2003 system where they registered as four separate 250GB hard disks.
Using the open-source Iometer performance utility we assigned a disk worker to each drive and using 64KB transfer requests and a 100 per cent sequential distribution we saw an average overall throughput of 98MB/s – around 25MB/s for each disk. During the test we found local processing overheads incurred by the software iSCSI initiator to be low with CPU utilisation settling at around 7.5 per cent. Next we created a four disk RAID-0 striped array in software on the test server and rerunning Iometer saw it report an average throughput of 65MB/s.
As one of the first examples of iSCSI network storage, the REO Series RA2000 will be a tough act to follow. Once you get your head around the concept of iSCSI initiators and targets, and the complex naming procedures that the standard’s body insists on, it’s actually relatively simple to set up and use. Performance may not be in the realms of Fibre Channel SAN storage but larger businesses looking for a means to speed up the backup process will find the price tag far more appealing.
By using the existing network infrastructure, iSCSI is so much easier to implement than Fibre Channel SANs. Performance may not be as good but it is nowhere near as costly and is easier to manage. Overland has focused on accelerating the backup process and the REO products look like ideal storage alternatives for enterprises and medium-sized businesses.