The Linear Tape Open Consortium has announced two more LTO tape generations, taking capacity up to 32TB compressed with LTO-8.

It has achieved this with an increased compression history buffer. It says that testing shows this can improve compression rates from the existing 2:1 to 2.5:1. Consequently raw tape capacities grow less than compressed capacities with the generations.

LTO-5, the current generation, offers 1.4TB raw and 3TB compressed. The coming LTO-6 has had its capacity for compressed data increased with the expanded compression history buffer, and it will now offer 3.2TB raw and 8TB compressed capacity.

LTO-7 will offer 6.4TB raw and 16TB compressed, with LTO-8 capping the family at 12.8TB raw and 32TB compressed.

Data rates will also increase, with the larger compression history buffer increasing the compressed data rate faster than the native data rate. LTO-5 offers up to - all these numbers are "up to" - 140MB/sec (280MB/sec compressed) with LTO-6 delivering 210MB/sec (525MB/sec compressed). The LTO-7 numbers are 315MB/sec native and 788MB/sec compressed with LTO-8 doing 472MB/sec native and 1.18GB/sec compressed.

The arrival dates of the new formats are not predicted by the LTO Consortium. If we apply a 2.5-years-between-generations rule of thumb starting from LTO-5 now, we get LTO-6 in late 2012, LTO-7 in early 2015, and LTO-8 in late 2017.

Nothing has been said about increasing tape media length or upping tape's speed through the read/write heads, so it looks as if the increased native capacity and I/O rate are going to come from having more tracks and/or smaller bits on the media. The media manufacturers must have agreed that they can develop the media to these levels so we're all headed for whacking great tape capacities.

Existing and happy LTO customers and product suppliers can relax, content that they won't run out of capacity for the next seven years or so. By 2015 it should be much clearer how disk storage of backup and archive data, either in customers' premises or the cloud, is affecting tape data storage usage, and the LTO consortium members - HP, IBM and Quantum - can form a view about whether even more LTO generations are needed. ®