Perhaps the most significant thing about iSCSI is that it gives a whole new class of servers access to networked storage, and StorageTek is now taking it a step further, using it to let clients access that storage too. In doing so, it reminds us that the real issue in data protection is not backup per se, but how quickly, easily and cheaply lost data can be recovered and restored.

The ideas behind StorageTek's EchoView E400 Data Protection Appliance are not new of themselves, but the company has rolled several of them together to add a new layer to the storage cake. The device keeps a running copy of the main disk storage, time-stamping and copying updates as they occur so it can recreate each protected volume as it appeared at a specific time.

StorageTek product manager Martin Warren says that it is this ability to roll back that differentiates EchoView from other approaches to data protection such as replication or mirroring. "It's making continuous backups. The nearest competitor would be journalling software, but EchoView is cross platform and works for a multitude of applications," he adds.

On the downside, it requires dedicated Gigabit Ethernet cards and a software driver installed on each protected server, the driver intercepts and copies all disk writes, and asynchronously writes them over iSCSI to the appliance. Drivers are available for Solaris and Windows 2000. By comparison, replication and mirroring can be done within the storage network or subsystem, and transparently to the servers.

Creating real copy
One benefit of the EchoView approach is that the appliance keeps copies of files for days or weeks at a time, and thanks to the use of iSCSI, users can restore these for themselves. They can browse back through old versions of their data, before dragging the one they want back onto their desktop.

"EchoView protects data as soon as it is written, creating not a virtual copy as snapshot mechanisms do, but a real copy, isolated from the primary copy," says Warren.

Because it is isolated, it can also be used as a way of staging backups, with data being written from the EchoView copy straight to tape without interrupting the application server. StorageTek claims it has an advantage over snapshots for this purpose, because snapshots usually share storage with the working volumes, so a backup from a snapshot can still adversely affect application performance.

The device is based around a quad-processor Intel server equipped with SCSI disks; the next version will cut cost by using StorageTek's new Bladestore storage, which uses cheaper ATA disks. StorageTek has added spice to it with a QLogic TCP/IP Offload Engine, or TOE: this is a Gigabit Ethernet card with its own processor that processes iSCSI packets on the host's behalf.

The first version can protect 400GB of application storage at a cost of $125 per GB. Warren says that larger and smaller models will follow, with the next being in the 1TB region. More server operating systems will be supported too, he says, and Fibre Channel attachment could be added for the larger models.