Review: Tandberg 420LTO tape backup drive

A common problem with small business servers is lack of space for a tape drive with, often, just a single half-height bay to play with.

Drives of that size tend to be limited in both performance and capacity, making backup labour intensive and time consuming. However, that isn’t the case with the Tandberg 420LTO, which slips easily into a half-height slot and yet supports the popular LTO (Linear Tape Open) Ultrium recording format.

The Tandberg 420LTO is an LTO2 drive. Not quite state of the art, as LTO3 drives have been around for some time now, but good value at about half the price.

Plus it can still cram a good 200GB of data onto each cartridge, rising to a theoretical maximum of 400GB if the claimed 2:1 compression ratio were to be achieved.

However, don’t expect to get that figure, as a lot of files will be compressed already and of those that aren’t few will be reduced by the full amount.

Still, given the mix of data found on most file servers you can comfortably expect to get around 300GB per tape – about how much data you’ll find on most small business networks.

And that means being able to fit a full backup onto a single cartridge while, if you want to handle more, autoloaders based on the Tandberg drive are also available.

On the performance front, the maximum transfer rate is a creditable 24Mbytes/sec, equivalent to 48Mbytes/sec when the 2:1 compression ratio is achieved. Again, you can’t just take the figures at face value.

The Ultra160 SCSI interface is more than fast enough (160Mbytes/sec), but the speed of the backup application can have a big impact, as can the specification of the host server, especially the storage sub-system.

Indeed, on an entry-level server, the speed at which data can be read from the hard disk is likely to be the main limiting factor – not the speed at which that data can be written to tape.

To give you an idea of what might be possible in practice, we installed the Tandberg drive into a typical small business server equipped with a single Intel Xeon processor, 1GB of Ram and a 200GB (Serial ATA) Sata disk array.

We then ran a backup using CA’s Brightstor Arcserve 11 software – a process that took a little over two hours with this setup, at an average transfer rate of 26.25Mbytes/sec.

Not as fast as with an LTO3 drive, but impressive nonetheless, especially given the relatively low price of the hardware.

Similarly priced half-height DLT drives, for example, would take a lot longer and can fit a lot less data onto a cartridge, while the much cheaper DAT products are slower still and currently max out at 72GB per tape.

Cartridge prices vary, of course, depending on the vendor involved, but we found Imation branded tapes on offer at £27.03 (£23 ex VAT), which is about what you’d pay for alternative DLT cartridges, with the ability to store a lot more data on each one.

We tested a bare drive designed to fit inside a server, so you’ll have to factor in the cost of cabling and backup software on top of the price given.

However, an external drive with its own power supply is also available, plus we were able to find vendors offering bundles that include the software, cables and tape cartridges required.