#rev 2020-09-03 davidsch
#rev 2018-09-03 mreimers

== LTS Archive ==

LTS (Long Term Storage) is a data archive service hosted by the central IT services of ETHZ (Informatikdienste, ID). More information about the LTS service can be found on [[https://www.ethz.ch/services/de/it-services/katalog/speicher/lts.html|here]]. Basically, LTS works like a [[https://en.wikipedia.org/wiki/Write_once_read_many|WORM file system]], i.e "Write Once Read Many". As a consequence, you may not alter (modify, delete, move, rename and so on) your archived files once that have been sucessfully transferred and stored on the LTS.

LTS is accessible via both NFS and CIFS (SMB) protocols. Note that both protocol backends on the LTS (NFS/ CIFS) are autonomous devices. This means that one might use either NFS or CIFS to access LTS data (but not both of them).

== Purpose ==
The LTS archive system is intended as a final storage for thesis, projects and other invariant data. It is '''not''' a backup system.

== Access ==
Although the LTS archive is hosted by ID, access to it is granted by ISG D-ITET only! A special fee-based ITET account is required. Due to its design as a long term storage, access is provided to nonpersonal accounts only. In practice, each laboratory or group is entitled to request a special LTS account. The account's credentials are hold by the person in charge, e.g. professor, group leader or local IT-administrator. In some exceptional cases, access is also granted to a project account.

For any questions concerning the LTS archive, write an email to [[mailto:support@ee.ethz.ch|support@ee.ethz.ch]].

== Usage ==
The usage of LTS causes some strict requirements and limitations:
 * Access protocol via ETH network is either NFS or CIFS (no concurrent access)
 * Data must be packed in large archive files (e.g. TAR, ZIP etc.)
 * Data for such archive files must be collected and prepared in a pre-processing task (best on local scratch disk). This must not be done on the LTS.
 * Allowed archive file sizes: less than 2TB, but at least 5GB (best between 10GB and 200 GB)
 * No data modification/ appending possible after sucessful archive transfer to the LTS (data is invariant)
 * LTS does not provide any mechanism against accidential data loss (i.e. no backup is made)
 * Data deletion on LTS is not possible on LTS (in exceptional cases, a removal request can be sent to central IT helpdesk)
 * Meta information can be stored within file name only
 * File/ directory name length is limited to 255 characters
 * Total path length is limited to 3900 characters
 * Do not work on LTS data directly (i.e. via NFS/ CIFS share). If you need data from LTS for work, copy it back first to your local disk, then start working on that copy.

== Best Practice ==

 * On the NFS share: Copy the preprocessed data from a local storage to LTS via `cp`. Using `rsync` with default options is not recommended, as it creates temporary intermediate files which are then renamed on the LTS storage, breaking the LTS use case. If using `rsync` is required then use `--inplace`.
 * Perform checksum verification on source and target files for every file which is stored on the LTS archive.