# Replication Workflows
LIGO and Virgo data is replicated to a variety of Tier-1 or Tier-2 facilities
which are managed by LIGO or Virgo themselves, and to smaller Tier-3 or 4
facilities managed by partner institutions (Tier definitions available in
LIGO-M0900325).  Individual sites subscribe to specific datasets or
collections of datasets, as defined above.   Replication policy is generally a
function of file type:

 * Raw Frames: each detector site (LHO, LLO) stores its own raw frames on tape.
 Each sites’ raw frames are also replicated to tape at CIT, yielding 2 tape
 replicas of each detector’s raw frames.  
 * HOFT, RDS & SFTs: again, each detector site (LHO and LLO) hosts its own tape
 replicas of these and the other site’s data, and both detectors’ data is
 replicated to tape at CIT, yielding 3 tape replicas of all data.   Various
 other Tier-N sites throughout the LDG “subscribe” to other datasets of
 interest. 

In summary, all raw frames are replicated to tape at each detector site and to
CIT, while most other Tier-N sites subscribe to subsets of the data, often
opting for more recent sets of HOFT.

For a rolling buffer of data, the rucio frame replication workflow follows the
procedure:
 1. Create a new dataset in rucio (E.g., `O3:H-H1_HOFT_C01`)
 1. Add a rucio replication rule to replicate `O3:H-H1_HOFT_C01` to desired Rucio Storage Element (RSE) (E.g., `LIGO-CIT`)
 1. Begin frame production:
  1. Files written to disk at the instrument site (E.g., LHO -> /archive/frames)
  1. LDAS diskcache daemon updates the diskcache file
  1. `gwrucio_registrar` reads diskcache, registers new files and attaches them to the desired dataset.
  1. The rucio replication daemons contact an [FTS server](http://fts.web.cern.ch/) 
  to initiate 3rd party transfers to replicate dataset to desired RSEs.

Data can also be registered statically from the command line or a list in a
text file.  See the example-workflows for specific examples.

See also: [rucio
docs](https://rucio.readthedocs.io/en/latest/replica_workflow.html) for general
replication workflows in rucio.