Differential Data Rates Table 2 shows the differential data rate for various output devices, for a range of blocksizes. The default blocksize of 10KB always results in inferior performance. If real, this is probably related to the size of the buffer in the tape drive. It is possible that higher-speed tape drives will be more subject to performance degradation due to FDDI delays. Investigation with an ethernet packet sniffer indicates that there is an interaction between blocksize and tcp buffer size which kills peformance at certain blocksizes.
More study is indicated.
The speed limitations imposed by ethernet probably cause the 8mm tape drive to experience frequent and substantial repositioning delays. Thus, the delays from tape and ethernet limitations inract, and the resultant speed is substantially slower than either one individually. Raw Data Click here for the raw results for all the individual test passes. The real-life dumps were performed on active systems, where other users may have been accessing the disk drives while the dumps were being performed. Likewise, network activity may have been greater in the real-life dumps.