When the demise of the DDS tape format was announced by Hewlett Packard, Sony and Seagate mid-2001, it came as a big shock as it commanded the biggest slice of the small to medium backup market. Even now it still accounts for around 50 percent of this market so it isn’t a surprise to see the format being resurrected this year with the introduction of the DAT72. Only HP and Seagate have continued the DDS partnership as Sony opted out preferring to develop its own long-established AIT format. However, Sony did deliver a parting shot as it co-owns the DDS logo and has refused to allow HP and Seagate to call this fifth generation DDS-5. One of the reasons Sony gave for discontinuing DDS was that the physical size of the compact 4mm media left little room for expansion. HP overcame these limitations by modifying the head geometry of DDS-4 to allow track density to be improved. Tape thickness was also reduced allowing the media length of DDS-4 cartridges to be increased from 155 metres to 170 metres. These changes provide a modest increase in native capacity to 36GB but DAT72 is unique as this is the first time a new tape format generation has not delivered a performance improvement. Consequently, all you get is the same pedestrian 3MB/sec native transfer rates of DDS-4. Test low-down
To test the DAT72 we installed it on a Pentium III 866MHz system with Windows 2000 Server/SP3 loaded while the backup software used was Computer Associates ARCserve 9 and Veritas Backup Exec 9. The storage subsystem comprised an Ultra160 SCSI hard disk and Adaptec controller whilst the tape drive was connected to a dedicated Ultra160 PCI card. We used a 5GB mixture of data to represent the average departmental server. Backup Exec produced the best results with it reporting an average data transfer rate of 209MB/min whilst securing 5GB of test data, 229MB/min during the tape verification run and 227MB/min when restoring the data to its original location. ARCserve proved to be noticeably slower with it delivering speeds of 182MB/min for backup, 181MB/min for the tape to disk verification and 183MB/min during the restore test. While it’s reassuring to see everyone’s favourite tape format dragged back from the precipice the mediocre improvements don’t inspire confidence as storage on the average workstation and departmental server has grown far beyond the native capacity of DAT72. The lack of a performance boost is worrying and, at the time of writing, HP and Seagate had not announced a product roadmap so there is no guarantee that there will be another generation after this. Even so, many smaller businesses still find DDS-4 satisfies their backup demands and DAT72 will allow them to put off a costly move to a new format. On the other hand, those that are looking for a new format to migrate to will find there is a wide range of options with Sony’s AIT-1 and AIT-2 and Exabyte’s VXA drives at the top of the list.