Data Movement Configuration

Data Movement can be configured in multiple ways:

1. Server side
2. Per Copy Offload API Request arguments

The first method is a "global" configuration - it affects all data movement operations. The second is done per the Copy Offload API, which allows for some configuration on a per-case basis, but is limited in scope. Both methods are meant to work in tandem.

Server Side ConfigMap

The server side configuration is done via the nnf-dm-config config map:

kubectl -n nnf-dm-system get configmap nnf-dm-config

The config map allows you to configure the following:

Setting	Description
slots	The number of slots specified in the MPI hostfile. A value less than 1 disables the use of slots in the hostfile.
maxSlots	The number of max_slots specified in the MPI hostfile. A value less than 1 disables the use of max_slots in the hostfile.
command	The full command to execute data movement. More detail in the following section.
progressIntervalSeconds	interval to collect the progress data from the dcp command.

command

The full data movement command can be set here. By default, Data Movement uses mpirun to run dcp to perform the data movement. Changing the command is useful for tweaking mpirun or dcp options or to replace the command with something that can aid in debugging (e.g. hostname).

mpirun uses hostfiles to list the hosts to launch dcp on. This hostfile is created for each Data Movement operation, and it uses the config map to set the slots and maxSlots for each host (i.e. NNF node) in the hostfile. The number of slots/maxSlots is the same for every host in the hostfile.

Additionally, Data Movement uses substitution to fill in dynamic information for each Data Movement operation. Each of these must be present in the command for Data Movement to work properly when using mpirun and dcp:

VAR	Description
$HOSTFILE	hostfile that is created and used for mpirun.
$UID	User ID that is inherited from the Workflow.
$GID	Group ID that is inherited from the Workflow.
$SRC	source for the data movement.
$DEST	destination for the data movement.

By default, the command will look something like the following. Please see the config map itself for the most up to date default command:

mpirun --allow-run-as-root --hostfile $HOSTFILE dcp --progress 1 --uid $UID --gid $GID $SRC $DEST

Profiles

Note: This feature is not fully implemented, but is present in the nnf-dm-config config map. Only the default profile is used, and it must be present in the configuration. Once the feature is implemented, a user will be able to select a profile using #DW directives and/or the Copy Offload API. Right now, users can add additional profiles into the config map, but the only way to use them would be to rename one of them to be default.

slots, maxSlots, and command can be stored in Data Movement profiles. These profiles are available for a quick way to switch between different settings for a particular workflow.

Example profile:

profiles:
  default:
      slots: 8
      maxSlots: 0
      command: mpirun --allow-run-as-root --hostfile $HOSTFILE dcp --progress 1 --uid $UID --gid $GID $SRC $DEST

Copy Offload API Daemon

The CreateRequest API call that is used to create Data Movement with the Copy Offload API has some options to allow a user to specify some options for that particular Data Movement. These settings are on a per-request basis.

See the CreateRequest API definition for what can be configured.