Tape storage

 

Introduction

Tremendous progress has been made in tape storage technology since the announcement of IBM's first tape drive—the IBM 726 tape unit—in 1952. The IBM 726, depicted in Figure 1, was able to store data at 6.1 kB/s at an areal density of 1400 bit/in2 and had a capacity of approximately 2.3 MB.

In 2011, IBM began shipping the TS1140 tape drive with an uncompressed capacity of 4 TB in a single tape cartridge and a native sustained data transfer rate of 250 MB/s, depicted in Figure 2. This translates into an improvement of 10,000× in data rate and more than 1,000,000× in areal density (i.e. more than 6 orders of magnitude). IBM's latest tape library, the TS3500, is depicted in Figure 3 and can store up to 900 PB of uncompressed TS1140 data.

Currently, tape systems play a central role in archival and disaster recovery applications and are the technology of choice for tertiary bulk storage in enterprise systems due to their very low total cost of ownership, low power consumption, high volumetric density and very high reliability. Tape systems also become an integral part of active archives, in which data can be migrated to the most appropriate storage tier (e.g. SSD, HDD, tape) and where users can access data from all storage tiers through a common filesystem that represents all the tiers as a single namespace.

In order to maintain their dominance in these applications, tape-based storage systems need to match or exceed the performance growth of hard-disk systems, while maintaining or improving their price/GByte advantage. Fortunately, there is still significant potential to continue scaling of tape technology.

For example, in 2010 in collaboration with FUJIFILM, IBM demonstrated the potential for recording at an areal density of 29.5 Gb/in2 using a prototype BaFe tape fabricated using low cost particulate coating technology [2011-2]. According to the 2012 Information Storage Industry Consortium (INSIC) tape road map, such an areal density will enable a cartridge capacity of 64 terabytes in the 2020 timeframe. Moreover, a recent feasibility study indicates that there is further potential to continue scaling tape towards areal densities of 100 Gb/in2 [2008-1].

This work clearly indicates that there is enormous potential to continue scaling tape systems for many years to come. However, maintaining both the growth in the areal density and data rate of tape systems while maintaining other desirable attributes such as backward compatibility, poses complex technical challenges that span diverse disciplines including signal processing and servo control, materials science, magnetic recording physics and mechatronics.

IBM 726 tape unit from 1952 with a reel capacity of 2.3 MB.
TS1140 tape drive from 2011
TS3500 tape library