Lower than expected transfer rates may be observed when duplicating to tape or performing large scale restores from various types of deduplication storage.
Duplicating to tape is particularly sensitive to low transfer rates. Data transfer to physical tape is optimal when the source data streaming rate matches or exceeds the minimum streaming rate of the physical tape drive. If the transfer rate from the source storage is less than this minimum streaming rate, the tape drive may write even slower than the source data streaming rate.
This issue also affects NetBackup 5200/5220 appliances, version 2.0
When duplicating from any deduplication storage to tape Symantec recommends following Best Practices, which are described in the white paper linked below.
Media Server Deduplication improvements are available in the NetBackup 220.127.116.11 Maintenance Update. Information on downloading this update, as well as the Release Notes, which include documentation regarding these improvements are all linked in the Related Articles section below.
This issue is also addressed in the 2.0.1 patch for NetBackup 5200/5220 appliances, also available via the link included in the Related Articles section.