IT Services



Acceptable Use Guidelines for using HFS Backup Services


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Guidelines for Acceptable Use of HFS Backup Services

The HFS is a valuable University resource with a large but ultimately finite capacity. Certain guidelines are therefore required to ensure the fair use of its resources so that the facility can be used as widely as possible.

We constantly review our operational limits in the light of available resources and capabilities. Currently we recommend a single backup account store no more than 10TB of data. We are aware that some systems exist which manage much greater amounts, but unfortunately our resources do not extend to covering these. Neither do we support 'partitioning' such systems into multiple backup accounts to circumvent the 10TB limit and so such systems must therefore look to implementing their own backup solution.

Independent of the amount of data stored, where a large number of files are held locally, we strongly recommend, and may insist, that these are either bundled into a local archive file prior to sending to the HFS or the local disk is re-partitioned into smaller filesystem/volume/drive partitions. There is no magic limit here, as the requirement for this depends partially on the client machine's own resources and ability to sort large numbers of files. Typically, the figure revolves around several million file objects in any one partition.

Additionally we insist that our clients:
  1. Connect to our service and upload data at a reasonable speed - see below, 1. Connection speed to the HFS.
  2. Try to avoid backing-up some types of information - see below, 2. What to exclude from backups.
  3. Try to ensure that only University work-related data is included in the backup - see 2. What to exclude from backups.
  4. Try to avoid backing-up data from duplicate locations - see below, 3. Moving data around.


1. Connection speed to the HFS

Long slow backups can cause considerable problems with the service: they lock server resources that need to be spread across many clients. Consequently, we demand that clients upload data at a reasonable rate such that the upload of their data does not take an unreasonable amount of time. At 10 hours a client session will be cancelled. It is to be noted that this is an extreme measure enacted in order to manage server resources - it should not be seen as a boundary limit below which all backups will be tolerated. This is particularly important for 'server'-level clients. The guiding principle is: if you have a lot of data to backup, then you must have the machine resources and network bandwidth to do it. Please ensure that, as well as sufficient network bandwidth, a server client has the CPU and memory resources to sort and process the number of files it has on it. As a guide the TSM client requires 300 bytes of memory per file, so a partition of 3 million files will require just short of 1GB of memory. We would expect most server clients to complete a backup of 300GB of data within 5 hours - equating to an upload speed of 16.67MB/sec. Should a client consistently fail to complete its backups, and there is no transient error situation (e.g. network misconfiguration) as the cause, then we reserve the right to exclude this client from the service. Current limits are documented in our FAQ items What limits are there on use of the HFS ? and How much data can I back up ?. It should be noted that there is currently no maximum connection speed limit.



2. What to exclude from backups

The HFS backup service is intended for active data that is in use by current members of the University. Certain files types which should not be backed up are excluded from backup by the HFS set of default exclusions. However, these exclusions cannot catch all examples. Therefore we ask that users ensure that the following data are excluded from HFS Backup on all client machines they own or manage.

Examples of how to exclude files and folders from HFS backups can be found in our page on how to exclude files and folders from backup. Further help can be obtained by contacting hfs@ox.ac.uk.



3. Moving data around

The TSM software recognises a file moved to a new location on a system as a new file and thus a candidate for backup. A renamed mountpoint, drive, volume or partition will also, unless specifically excluded, occasion a fresh backup of all data on it. Windows drives derive their name from the Windows computer name, thus a change to this (which in itself might be due to a change in the machine's TCP/IP Name), can act as a partition rename. In these cases the data is in effect copied again and hence lies duplicate within the HFS Backup system. It is thus imperative that users avoid unnecessary moves and renames.

In cases where you do anticipate essential large-scale moves or renames of your local datastore, please contact hfs@ox.ac.uk beforehand so that we may manage this.



4. Additionally

Additionally, we may insist on local measures being implemented in order that the backup or archival of that data does not consume a large amount of (HFS) system resources. These local measures may include, but are not limited to:- excluding files, re-partitioning into smaller filesystem/volume/drive partitions or pre-processing files before backup or archive.