Online Backup Considerations
We've looked at the Zettabyte features and certainly agree that the concept makes a lot of sense. It integrates smoothly with your existing infrastructure and only requires an Internet connection to work. This, however can be the problem, because with ADSL and other Internet connections, upstream bandwidth is usually only a fraction of downstream bandwidth. Zettabyte says it provides 250 Mbit/s bandwidth, which is certainly fast enough to restore a lot of data to your zBox, but the backup process depends on the capabilities of your Internet connection. SDSL and VDSL offer equal upstream and downstream bandwidth, as do some cable modems, but VDSL at up to 50 Mbit/s is rather expensive.
Let's look at an example. If you put 50 GB of data on your zBox within a short period of time, the system will start backing up the data to the online services. The following table shows how long the data upload will take with different mainstream Internet connection options:
| Internet Connection Type | Entry-level DSL (2 MBit package) | Mainstream DSL (6 MBit package) | High-end DSL (10-16 MBit package) | Other options | |
|---|---|---|---|---|---|
| Typical Upstream | 256 kBit/s | 768 kBit/s | 1 Mbit/s | 2 Mbit/s | 10 MBit/s |
| Effective Upstream Bandwidth | ~ 28 kB/s | ~ 90 kB/s | ~ 120 kB/s | ~ 230 kB/s | ~ 1200 kB/s |
| Time Required for 50 GB | 520 hours(~22 days) | 161 hours(~7 days) | 121 hours(~5 days) | 60 hours(2-3 days) | 12 hours |
| Time Required for 300 GB | ~130 days | ~42 days | ~ 30 days | ~ 15 days | 3 days |
Remember that these durations apply to data uploads from mainstream Internet connections as you will find them at home and in small businesses. The numbers mean that backing up as much as 300 GB is ultimately useless with low-budget ADSL Internet connections that give you only a few hundred kilobits per second of upstream. Any backup that takes more than a few days should already be considered impractical, because the system might be busy copying lots of data for days, without updating files that have already been modified - or the system might be updating current files, but fail to backup other data. The good news is that the durations refer to the first backup, as all modifications will certainly finish much quicker.
The examples above also represent a perfect world scenario, where the Internet line is being used for nothing else, and where you don't experience DSL disconnects. If you really want to use the Zettabyte service with serious online backup in mind, we recommend at least 2 Mbit/s upstream, and the more, the better. Incidentally, this is also the reason why online storage providers don't hesitate to offer double digit gigabyte capacities for free: it just takes a long while for most users to fill it up.
