When planning your backup strategy you need to consider the path that data takes to your backup servers and from there to your tape drives or disks. Whichever is the slowest point in the chain will determine just how fast your backups can run.
Below are some metrics that give rough throughputs for networks, backup devices etc to help you plan your backup and know in advance just what sort of throughput you are likely to get. All you then need to do is multiply the slowest link in your chain by the number of hours of your backup window and then you know just how much data you will be able to backup – remember that bonding cards together or adding backup devices to a tape library will increase your data throughput (simply multiply the figures below).
Network Transfer Rates
| Network Type | Theoretical Rate | Realistic Throughput | Realistic Rate |
| 10 Base-T | 10 Mbps or 1.25 MB/sec |
40 – 50 percent | 500 KB/sec or 1.8 GB/hr |
| 100 Base-T | 100 Mbps or 12.55 MB/sec |
80 percent | 10 MB/sec or 36 GB/hr |
| 1 Gigabit | 1000 Mbps or 125 MB/sec |
70 percent | 87.5 MB/sec or 315 GB/hr |
SCSI Transfer Rates
| Version | Bus Width | Approximate Maximum Data-Transfer Rate |
| Wide Ultra SCSI | 16 bits | 40 MB/sec or 144 GB/hour |
| Ultra2 SCSI | 8 buts | 40 MB/sec or 144 GB/hour |
| Wide Ultra2 SCSI | 16 bits | 80 MB/sec or 288 GB/hour |
| Ultra160 SCSI | 16 bits | 160 MB/sec or 576 GB/hour |
| Ultra320 SCSI | 16 bits | 320 MB/sec or 1,152 GB/hour |
Fibre Channel Transfer Rates
| Version | Bus Width | Approximate Maximum Data-Transfer Rate |
| Fibre Channel | 1 Gbps | 100 MB/sec or 360 GB/hour |
| Fibre Channel | 2 Gbps | 200 MB/sec or 720 GB/hour |
| Fibre Channel | 4 Gbps | 400 MB/sec or 1,440 GB/hour |
| Fibre Channel | 8 Gbps | 800 MB/sec or 2,880 GB/hour |
Tape Drives
| Device Type | Approximate Transfer Rate | Maximum Capacity |
| DDS-4 | 6.0 MB/sec or 21.6 GB/hour | 40GB |
| AIT-2 | 12.0 MB/sec or 43.2 GB/hour | 100 GB |
| AIT-3 | 31.2 MB/sec or 112.3 GB/hour | 260 GB |
| DLT 7000 | 10.0 MB/sec or 36.0 GB/hour | 70 GB |
| DLT 8000 | 12.0 MB/sec or 43.2 GB/hour | 80 GB |
| Super DLT | 24.0 MB/sec or 86.4 GB/hour | 220 GB |
| Mammoth-2 | 24.0 MB/sec or 86.4 GB/hour | 160 GB |
| Ultrium (LTO) | 30.0 MB/sec or 108.0 GB/hour | 200 GB |
| IBM 9890 | 20.0 MB/sec or 72.0 GB/hour | 40 GB |
| IBM 3590E | 15.0 MB/sec or 54.0 GB/hour | 60 GB |
| LTO2 | 68.0 MB/sec or 245.0 GB/hour | 400 GB |
| LTO3 | 160.0 MB/sec or 576.0 GB/hour | 800 GB |
| LT04 | 240.0 MB/sec or 864.0 GB/hour | 1.6 TB |
| DLTS4 | 320.0 MB/sec or 1,152 GB/hour | 1.6 TB |
So, don’t buy a DLTS4 drive to run over a 1GB link, you may as well save some money and buy a less capable drive as your link will slow you down. And do consider streaming multiple backups to the same backup device or using multiple older backup devices to take account of faster links.
Philip Flint 
Very useful, I was trying to work out whether transfer rates between our primary and secondary servers were realistic, they are. Cheers
p.s. Yatesey directed me here
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– Lucas
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