Mark

It's not really a question of reliable enough more a question of how much data you need to backup, when it needs backing up and how important this data is.

If the combined backup data and normal business traffic is more than your links bandwidth at the primary data center then something has to give. If you prioritise business traffic then there is the possibility your backups might not complete in time. If you prioritise backup data there is the possibility of impacting on business traffic.

Also it depends on how you intend to use the backup data ie. how quickly do you need the backup data to be written to the secondary data center. Do you intend to fail over automatically if the primary data center fails.

Personally in the Enterprises i have worked there were standard approaches

1) If an overnight backup is good enough then use the production links as long as the backup window does not overlap with production hours

2) If backups are needed throughout the day but are in a drip feed form where there is still available bandwidth and there is no need for a guaranteed write time then you can use production links but you need to closely monitor the backup traffic.

3) If a guarantee is needed for write time eg database traffic use dedicated link or use QOS to priortise the traffic but it is unlikely the business will want it's core hours traffic disrupted.

4) If backups must run during the day but the backup + business traffic exceed the bandwidth available then either -

i) if backup traffic does not require quarantees you could look to use QOS to ensure the backup traffic does not impact business traffic

ii) if guarantees are required then dedicated link.

Jon