--- group: composite_volume --- The OCF composite volume provides functionality of composing mutiple OCF volume instances into one bigger volume. The component volumes are linearly mapped into address space of the composite volume (unlike RAID0, which uses interleaved mapping a.k.a. striping). +-----------------------+---------------+-----------------------------+ | volume A | volume B | volume C | *-----------------------|---------------|-----------------------------+ LBA | 0 | 1 | 2 | 3 | 4 | 5 | 0 | 1 | 2 | 3 | 0 | 1 | 2 | 3 | 4 | 5 | +---------------------------------------------------------------------+ | composite volume | +---------------------------------------------------------------------+ LBA | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | +---------------------------------------------------------------------+ -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Creation of composite volume instance id: creation --- It shall be possible to create an instance of a composite volume using a constructor function. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Destruction of composite volume instance id: destruction --- It shall be possible to destroy an instance of a composite volume using standard ocf_volume API. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Adding new component volume id: adding_component_volume --- If shall be possible to add new component volume to the composite volume using dedicated function. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Instatiation of component volumes id: instatiation_component_volumes --- Adding component volume to composite volume shall automatically instatiate component volume based on type, uuid and volume_params parameters. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Destrution of component volumes id: destruction_component_volumes --- Component volume instances shall be destroyed on composite volume destruction. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Adding component volumes of different types id: component_volume_types --- It shall be possible to add component volumes of different volume types to single composite volume. The only requirement is that those types shall be registered within the same ocf_ctx. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Maximum number of composite volumes id: max_composite_volumes --- It shall be possible to add up to 16 component volumes to a single composite volume. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Volume API id: volume_api --- Composite volume shall conform to regular ocf_volume API. I.e. it shall be possible to perform on it following volume operations: open, close, get_max_io_size, get_length, submit_io, submit_flush and submit_discard. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Volume open id: volume_open --- Composite volume shall open all component volumes when it's being opened. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Volume close id: volume_close --- Composite volume shall close all component volumes when it's being closed. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Getting maximum io size id: get_max_io_size --- Composite volume shall report a maximum io size being the lowest maximum io size among all the component volumes. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Getting volume length id: get_length --- Composite volume shall report a lenght being a sum of lenghs of all component volumes. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Request passing id: request_passing --- Composite volume shall pass io, flush and discard request or its fragments to component volumes based on their mapping. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: IO Flags passing id: io_flags_passing --- Composite volume shall pass all IO flags associated with request to all requests issued to component volumes as part of fulfilling the master request. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: I/O request completion id: io_request_completion --- The I/O request shall be completed only when all sub-I/Os submitted to component volumes are completed. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: I/O error handling id: io_error_handling --- If I/O error occures on any I/O request submitted to composite volume, that error shall be passed to the completion of the original I/O request. If multiple sub-I/Os reported errors, the first error that occured shall be passed to the completion of the original I/O request. -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- title: Attaching/loading the cache id: cache_attach_load --- It shall be possible to attach/load the cache using instance of a composite volume.