QStar Archive Manager and its enhanced sister product Archive Replicator create solutions such as Tape-as-NAS, Tape-as-Cloud and Cloud Gateway for archiving purposes. Both use a “cache” when moving data into and out of the archive. The archive can consist of one or more technologies, including tape, cloud, disk and optical. In most circumstances, the cache is small but fast, now most often NVMe disk, to facilitate the rapid movement of files to the chosen archive technology. The cache will do two operations (a write followed by a read) for every one write to the archive and so MUST be at least double the archive performance. New data automatically over-writes the oldest files and in this way the cache is kept as full as possible with the most recently written or read files.

The cache also contains a database of all file metadata and extended attributes, plus specific additional data, such as the barcode label of the tape media used, to facilitate finding offline media and the starting block address on the tape media to speed reads. This database is periodically written to the archive as well and can be recovered from the archive for disaster recovery purposes.

The cache location and its associated archive(s), something QStar calls an Integral Volume, as it integrates the two storage technologies into one, is made available to other applications or users through one or all of the following: a Windows drive letter or SMB Share, a Linux Mount or NFS share, or an S3 Cloud bucket. For example, it is possible to write using a Windows SMB Share but read through an S3 browser application, if configured to do that.

There are a number of triggers that start and stop the writing of data from the cache to the archive. The first is a manual “archive” button that immediately starts the archive. The second is a timed mechanism that triggers the archive operation on a user defined schedule. The third and most often used is the High Primary Capacity (HPC) option. This is a watermark that triggers writing to the archive when the cache reaches a certain percentage full. It can be varied to prioritize reads over writes or writes over reads.

A new feature within Archive Manager v7.0 – launched at the beginning of 2021 – is the Cache Booster option. This typically allows two cache locations to be used, one small and very fast for writes and a second larger slower one for reads. The Cache Booster option can use a RAM disk or NVMe drive with relatively small capacities to rapidly write content to the archive at the maximum performance of the archive used. If the user wishes faster read response times, rather than waiting for tape media to load or pay Cloud egress fees, a relatively inexpensive SATA RAID disk set could also be used.