Virtuous data accesses in High-capacity Storage systems – VHS

Magnetic tapes have been used to store computer data since the 1950s, so the layman now
often considers it as an outdated technology. However, tape storage is still and will remain essential in
many fields such as academic research, international organisations or cloud companies . This dependency on tapes has motivated industrial efforts in
technology improvements, resulting in much faster data density progression on tape rather than on
disk. After recent breakthroughs in materials used, tape capacity is expected to witness a massive
leap in coming years, increasing to several hundreds of TB per tape. This evolution
will amplify the main benefits of tape storage (low energy consumption etc).

However, tapes have often been primarily considered for archiving cold data, because of their main
drawback: it takes around a minute to mount a tape from its shelf into a drive and position the
reading head before starting reading data. This explains the current lack of academic effort to optimize
relatively frequent data accesses. Nevertheless, more and more research projects require to handle
tremendous volumes of data, which are not only destined to be archived but also regularly accessed
for scientific analysis. Budget constraints impose the usage of tape storage, and optimizing tape data access therefore becomes more and more significant, and not limited to improving archive retrieval.

The general idea of the VHS project is to propose new interactions between resource management
and tape systems. Using filesystem on tapes, we plan to design novel data placement
strategies that will propose efficient data accesses by considering tapes at the level of the storage
hierarchy by optimizing its operational cost.
Our methodology starts from the tapes themselves, to better understand the physical processes involved in the different operations. Then, we will leverage this knowledge to derive interactions between tape and disk storage systems in order to improve data placement.