Product Reviews

Early adopters of VXA must have been getting worried of late, as the second generation of this tape format has taken far too long to materialise. Repositioned last year as a DDS replacement, the VXA-1 (see Enterprise, issue 64) was introduced in mid-1999 and offered a similar native performance to DDS-4, but a much higher 33GB of native storage on 8mm cartridges. More than three years on and we finally have VXA-2, which delivers a doubling in transfer rates to 6MB/sec, a capacity increase to a healthy native 80GB and, more importantly, remains firmly on a price par with DDS-4 drives.

The VXA format introduced three new technologies aimed at providing reliable data restoration. Discrete packet format (DPF) breaks data down into packets before writing them to the tape. During a read operation, the

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packets can be read back in any sequence as they're reassembled in the drive's buffer before being sent to the host. Packets that are correctly retrieved on the first pass of the head are stored in the buffer. Subsequent passes are carried out until all the packets are read and then the data string is assembled before being forwarded to the host. Variable speed operation (VSO) allows the drive to adjust tape speed to match the data flow and avoids the problem of the drive stopping and re-positioning the tape whenever the data flow is interrupted. During write operations, an overscan operation (OSO) is used to scan the data and re-write it if an error is detected.

For testing, we hooked the external drive up to a Pentium III/866 system with 512MB of memory and running Windows 2000 Server. Veritas Backup Exec 8.6 reported an average transfer rate of 366MB/min while securing 5GB of test data and 305MB/min for the tape read verification test. Data restoration was less impressive, as speed dropped to 299MB/min when returning the test data to its original location.

Competition for the DDS space has never been hotter and the VXA-2 is a fine performer at this price point, making it a top backup choice for small businesses looking to migrate from DDS. Storage capacity is also impressive, but our main worry is whether Exabyte will keep us waiting another three years for VXA-3.