Disk replacement for LTO tape18 March 2011
New UK company Disk Archive Corporation is offering an alternative to LTO tape for nearline archives, using low cost disk drives in a new architecture.The falling cost of disk drives means that today a 2 TB disk drive costs less than an LTO tape. Add in the mechanical complexity of a tape robot, and the cost differential becomes significant.The DAC Alto-100 provides 48 disk drives in a 5U cabinet. Rather than Raid protection, it simply uses multiple copies of a file to provide security. The argument is that, in a device like this, the chance of a second disk failing while rebuilding a Raid file after a first failure is high, leading the system to chase its tail and perhaps take as long as 24 hours to be restored.“Green” disk drives are used, which power down when not in use. As well as saving 500W in power consumption, it saves the equivalent amount in air conditioning. Performance is claimed to be equivalent to LTO tapes.A single frame, with 100 TB of storage, is priced at 34k euros. For larger capacities, devices can be daisy-chained. The system is already in use at a network of 10 regional news bureau in Russia.