Data I/O throughput speed of the HSM migration is strongly limited by the overhead of DCE/DFS caching disk, which is roughly 1-3 MB/sec[2]. We experienced various DCE timeout problem with HSM migration, until we modified the HSM algorithm. Nevertheless, the HSM migration with DCE/DFS environment is proven to be a viable solution for multi-user accesses under distributed environment.
The direct access method gives the highest performance of the DTF tape drive, which is roughly 12 MB/sec. Number of tape mount request was 36 times per day on average and number of file access requests was 233 times per day for January and February 1997. Tape mount time per request was 63 to 121 seconds (84.7 seconds in average).
The DTF drive is capable of high speed file mark indexing. File positioning time from the beginning of the tape to the bottom of the tape (40 GB) is roughly 160 seconds. Typical operations of file opening and closing take about 10 to 20 seconds.