Have you ever found yourself calculating how long your online backups will take to complete? The following table shows theoretical best-case data transfers rates (GB/Hr and GB/Day) for different speed Internet connections such as T1s, DS1s, OC3s, etc. where you can interpolate additional values when you know the speed of a specific user’s Internet connection:
kbps | mbps | KBs | MBs | Name | #GB/hour | #GB/day |
---|---|---|---|---|---|---|
64 | 0.063 | 8 | 0.008 | 0.03 | 0.66 | |
128 | 0.125 | 16 | 0.016 | 0.05 | 1.32 | |
256 | 0.250 | 32 | 0.031 | 0.11 | 2.64 | |
384 | 0.341 | 48 | 0.043 | 0.15 | 3.60 | |
512 | 0.512 | 64 | 0.064 | 0.23 | 5.40 | |
756 | 0.772 | 95 | 0.097 | 0.34 | 8.14 | |
1,581 | 1.544 | 198 | 0.193 | T1/DS1 | 0.68 | 16.28 |
5,120 | 5.000 | 640 | 0.625 | 2.20 | 52.73 | |
6,463 | 6.312 | 808 | 0.789 | T2/DS2 | 2.77 | 66.57 |
10,240 | 10.000 | 1,280 | 1.250 | 4.39 | 105.47 | |
45,810 | 44.736 | 5,726 | 5.592 | T3/DS3 | 19.66 | 471.83 |
51,200 | 50.000 | 6,400 | 6.250 | 21.97 | 527.34 | |
102,400 | 100.000 | 12,800 | 12.500 | 43.95 | 1,054.69 | |
158,106 | 154.400 | 19,763 | 19.300 | OC3 | 67.85 | 1,628.44 |
204,800 | 200.000 | 25,600 | 25.000 | 87.89 | 2,109.38 | |
280,756 | 274.176 | 35,095 | 34.272 | DS4 | 120.49 | 2,891.70 |
632,422 | 617.600 | 79,053 | 77.200 | OC12 | 271.41 | 6,513.75 |
1,024,000 | 1,000.000 | 128,000 | 125.000 | 1Gbs | 439.45 | 10,546.88 |
2,529,690 | 2,470.400 | 316,211 | 308.800 | OC48 | 1,085.63 | 26,055.00 |
10,118,758 | 9,881.600 | 1,264,845 | 1,235.200 | OC192 | 4,342.50 | 104,220.00 |

transfer speeds
But what is the client’s actual Internet speed? Is the rate that the ISP publishes real? It appears that some major ISPs are now allowing their client’s to burst to higher bandwidth speeds for short periods of time and then the ISP throttles the connection for sustained TCP connections (such as for your client’s backups and restores), and thus connection test speeds and (tested) ISP advertised speeds may not accurately reflect reality. Given this, how can one actually estimate how long a backup with take and what their actual Internet bandwidth is?
WholesaleBackup clients can test their actual upload and download speed to your backup servers from the software client on the “Remote Settings” tab! Furthermore, WholesaleBackup clients can also throttle their connection speed to your servers on the “Remote Settings” tab.

server volumes
In practice, an online backup will take longer than the theoretical maximums above due to the time to perform integrity checks, compression, encryption, and differentials as well as the latency of their Internet connection. WholesaleBackup’s offsite backup software provides an estimate (on the “Monitor” tab) of the time it will take to perform the backup, it is basically a worst-case estimate, and as one watches it one will see that, as time passes, the throughput typically improves dramatically and the estimated completion time gets better – this is due to optimizations we perform as the backup proceeds and the fact that its backs up the client’s largest files last and these make the best use of their Internet pipe.
Another related question, covered in a previous blog post entitled “Sizing your Internet Pipe for Your Online Backup Business” on WholesaleBackup.com, is how to calculate, from real-world experience, how much Internet bandwidth is required to run your own online backup business.