HSM is a large network disk, of unlimited size, accessible via Windows or Unix. It is a system which copies, onto magnetic tapes, the data that we want to archive over the long term. It is an archiving system which is duplicated in two of Ifremer's buildings, for greater security (protection against a major disaster). Data can be deposited and retrieved from these machines automatically. To put data on them and to be able to recover them, it is essential to be very rigorous in the ordering and classification of data and to strictly comply with the tree structure defined, to easily find the data.