Transtec Provigo 210

iSCSI is proving to be a popular choice for smaller businesses building low-cost storage networks, but Transtec's Provigo 210 shows it isn't the only solution. It inevitably brings yet another acronym to the table, but SoIP (storage over IP) offers a number of interesting possibilities, plus lower costs. Adaptec's Snap Server 210 (web ID: 94219) is one of a few products capable of delivering iSCSI target capabilities for less than a grand, but at a mere £430 for 1TB the 210 looks even better value.

Before we delve deeper into what's on offer, it's worth taking a closer look at Z-SAN, since it really is rather clever. The appliance uses a basic hardware controller, which runs a DHCP client that takes a base IP address for the controller and one for each of the four hard disks. As you create your volumes - coined "IP partitions" by Zetera - these will also require an IP address that makes them appear to the network as a new hard disk.

Each IP partition is assigned a unique LBA (logical block address) range - the same as used by hard disks to denote the physical location where data is to be written to or read from. The appliance then looks out for packets on the network that have a destination IP address that matches one of its partitions. Along with the payload, each packet contains an LBA range that determines where the data should be placed in the partition. Each client system requires a filter driver that converts file system commands into IP traffic, a SCSI mini-port driver and the bundled MySAN Storage Manager utility that allows users to manage partitions.

As with iSCSI targets, a Z-SAN partition appears to client systems as a locally attached hard disk. The user that created a partition can decide whether to share and password-protect it, and partitions can be expanded on-the-fly into available physical space. Another advantage is partition spanning, as you can add another appliance to the network and expand an existing partition into it. Even better is the fact that partitions can be striped or mirrored, and for the latter the mirror could be across two appliances. So far so good, but the appliance's hunger for IP addresses is an issue. For example, one appliance with six partitions will eat up 11 addresses. We tested using a pair of 210 appliances, and at one point our DHCP server had handed out more than 20 addresses.

The manager software and driver installation is handled neatly by a single routine. The manager then scans the network, displays all discovered appliances and lists accessible logical volumes. Now you can carve up physical space by creating partitions, entering a size and deciding which physical drives they're to be located on. During this process, you can opt for a single partition or go for a stripe, mirror or a RAID10 striped mirror. With the latter three options, you can have both associated partitions on the same drive or different ones within a single appliance, or you can select drives on separate appliances. If you want, you can even have a single partition broken up into smaller chunks of space and spanned across multiple drives. To allow multiple client systems to share a partition, you need to select the proprietary Z-FS file system format (not to be confused with Sun's ZFS) during creation. The appliance also supports NTFS, but this allows a partition to be accessed only by the system that created it.

Real-world performance isn't groundbreaking, since copying a 690MB video file from a Supermicro 3.2GHz Pentium D workstation to a standard Z-FS partition on the 210 delivered a 19.7MB/sec write speed, while retrieving the file returned a 21.6MB/sec read rate. NTFS partitions proved to be more capable, as both read and write speeds improved to 27.6MB/sec. The best speeds we achieved were with a four-drive spanned partition on one appliance, which returned a 28.8MB/sec read rate. We created a mirrored partition across two appliances and found this dropped read and write speeds to lows of 21.6MB/sec and 15.3MB/sec respectively.