Machines registered for TSM backup as servers benefit from a higher daily limit than desktop/laptop accounts, and have automatic scheduled backups six days a week. Before you register a TSM node for server backup, please ensure that the server conforms on the following points.
Owners of server accounts must be registered as University of Oxford IT Support Staff (ITSS). If you have a server to register for backup but you are not ITSS-registered, ask your local IT to register the server for you and to put your name as contact e-mail for the account.
TSM works on the principle of incremental forever, only sending new or changed data to the HFS. However, if a folder is moved or renamed then all the data below that level will be regarded as new, and will be resent to the HFS. Similarly, permissions changes usually occasion a data resend.
If your data is in need of rearrangement, we therefore request that you perform this work before your initial backup. Thereafter, it is best to keep large-scale changes to a minimum. On this subject please see further the section on our best practice page which details the changes that cause TSM to resend data to the HFS.
TSM processes data one partition at a time. If, therefore, you have a very large amount of data to back up - say, several terabytes - then TSM may find it difficult to process. This is especially noticeable if there is a large number of files in one partition - more than a few million - even if the quantity of data is low.
We therefore request that server account owners ensure that their data is appropriately arranged before the initial backup. If you have several terabytes of data or more than a few million files, have it spread across a number of partitions.
- If the machine contains millions of files, then TSM will require a large amount of RAM in order to be able to process them. If the quantity of RAM is not sufficient then the backup will stall. IBM state that TSM will use 300 bytes per file or directory, dependent on file name and pathname length, i.e. 300MB to process one million files. So, if a process on the client machine is limited to 2GB, then TSM would be limited to processing 7 million files in one filesystem/partition.
- If the quantity of data to be backed up is hundreds of gigabytes, then that will require adequate network bandwidth in order to complete in a timely manner. For normal servers which frequently back up large amounts of data we recommend a 1GB network connection to the University backbone network; for large servers, this is a requirement.