1. Remote backup to the HFS over VPN
In August 2010 the HFS started to offer a standalone service to provide members of the University with secure data backup from outside the University Network. As of February 2014 this service has now been integrated completely within the standard 'desktop/laptop' backup service. The practical consequence of this is users no longer have to choose between a backup service confined only to the University Network and remote backup over VPN, they can do both within the standard desktop backup service.
That said, there remain some important pre-requisites, service features and caveats to using the HFS service over VPN and we strongly encourage you to read the sections that address these below.
3. Service Features
4. Backup/Restore Speed
The key issue when accessing the HFS 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 limited and most 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 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 to the HFS 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 :
(8Mbps download/1Mbps upload)
|Wired University Network
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; or, in the case of a restore, for waiting for the HFS systems to load the required tape and locate the position of the data upon the tape.
5. Broadband Quotas
As part of the backup process the HFS servers send a list of files which have been previously backed up to the machine performing a backup. This list is then compared with the files found on the disk to determine which files have been changed, created or deleted. For machines with a large number of files this list can be very large. Repeated backups of systems with a large number of files via broadband may, counter-intuitively, cause problems by exceeding broadband download limits. For this reason we strongly recommend that all files except for one or two key directories are excluded from backup (see above), and for machines with lots of small files to back up, to take extra care if using the backup service over VPN.