The key issue when backing up or restoring using the HFS Spectrum Protect service from outside the University Network is the speed of the connection. Backups over Fibre-optic broadband will be of comparable speed to a wired connection to the University Network and thus pose no problem. However, the availability of such connections is not universal and many of us in the UK still have an ADSL broadband connection. Backups via ADSL Broadband connections are particularly slow as the upload speed of the connection is usually significantly slower than the download speed. For this reason, where you require a large amount of data to be backed-up (i.e. uploaded), we strongly recommend that the initial backup is carried out over a wired connection to the Oxford Network. Thereafter you can use backup-over-VPN for the small incremental backups of files as they change over time.
The download speed (restore) is usually ten times greater than the upload speed (backup) and occasionally the difference can be larger.
Approximate times for backup over VPN compared to over a wired connection to the University Network are given below :
|
Backup |
|
|
Restore |
|
|
|
10MB |
1GB |
10GB |
10MB |
1GB |
10GB |
ADSL Broadband
(17Mbps download/2Mbps upload)
|
13mins |
2hrs |
20hrs |
10mins |
20mins |
3hrs |
Wired University Network
Connection (100Mbps)
|
10mins |
15mins |
35mins |
10mins |
15mins |
35mins |
These figures include an approximation, in the case of backup, for starting the session with the HFS and scanning the disk for files to back up.