and its SATA disks have also advantages. It enables you to improve small file backups and fast single file restores.
If typical files were saved from MSA1000 to MSA1500, the maximum transfer rate was 19,47 MB/s. If saved from MSA1500 to Ultrium 960, the transfer rate was 45,06 MB/s. The transfer rate was higher, if the same files were directly saved from the MSA1000 to 2 SDLT 320 (62,87 MB/s) or 1 Ultrium 960 (91,97 MB/s). In this case, tape was faster than disk. Please check Table9, Table11, Table12 and Table15.
If small files were saved from MSA1000 to MSA1500, the maximum transfer rate was (12,22 MB/s). The transfer rate was slightly higher, if the same files were directly saved from the MSA1000 to SDLT 320 (12,56 MB/s) or Ultrium 960 (14,24 MB/s). But if saved from MSA1500 to Ultrium 960, the transfer rate increased to 43,37 MB/s. Please check Table9, Table11, Table12 and Table15. These results confirm that Advanced Backup to Disk improves small file backups and tape drive utilization by first staging to disk and then copying to tape.
Furthermore the backup of small files was tested with the slower RAID 1+0 and 3 Logical Arrays configuration to demonstrate the impact on the tape drives. If the disk array cannot provide data fast enough, the tape drive suffers from stopping and starting (start/stop mode), which shortens the media life through a large number of repositions (media passes). Therefore, slower tape drives stop less and could be faster than their faster counterparts. In this setup, double SDLT 320 showed the highest transfer rate with 48,55 MB/s. Ultrium 460 showed 42,33 MB/s and Ultrium 960 just 39,25 MB/s. The effect on the average CPU load was opposite. SDLT 320 showed 19%, Ultrium 460 17% and Ultrium 960 just 8%. Please check Table13 and Table14.
The file depot size plays an important role for the CPU utilization and the resulting performance. For the typical file backup (to file library), the default Maximum File Depot Size of 50 GB resulted in a transfer rate of 19,47 MB/s with an average CPU utilization of 12%. The reduced Maximum File Depot Size of 10 GB resulted in a transfer rate of 19,24 MB/s but with an average CPU utilization of just 4%.
Please check the next two figures and Table12.
Figure 35. Advanced Backup to Disk - Average CPU Utilization with 50 GB File Depot Size
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