FTI File Format

FTI File Format (FTI-FF)

Structure

The file format basic structure, consists of a meta block and a data block:

   +--------------+ +------------------------+
   |              | |                        |
   | FB           | | VB                     |
   |              | |                        |
   +--------------+ +------------------------+

The FB (file block) holds meta data related to the file whereas the VB (variable block) holds meta and actual data of the variables protected by FTI.

The FB has the following structure:

   FB {
       checksum         // Hash of the VDB block in hex representation (33 bytes) 
       hash             // Hash of FB without 'hash' in unsigned char (16 bytes) 
       ckptSize         // Size of actual data stored in file
       fs               // Size of FB + VB
       maxFs            // Maximum size of FB + VB in group
       ptFs             // Size of FB + VB of partner process
       timestamp        // Time in ns of FB block creation
   }

The VB block possesses the following sub structure:

   |<-------------------------------------------------- VB -------------------------------------------------->|
   #                                                                                                          #
   |<------------- VCB_1 --------------------------->|      |<------------- VCB_1 --------------------------->|
   #                                                 #      #                                                 #       
   +-------------------------------------------------+      +-------------------------------------------------+
   | +--------++-------------+      +--------------+ |      | +--------++-------------+      +--------------+ |
   | |        ||             |      |              | |      | |        ||             |      |              | |
   | | VMB_1  || VC_11       | ---- | VC_1k        | | ---- | | VMB_n  || VC_n1       | ---- | VC_nl        | |
   | |        ||             |      |              | |      | |        ||             |      |              | |
   | +--------++-------------+      +--------------+ |      | +--------++-------------+      +--------------+ |
   +-------------------------------------------------+      +-------------------------------------------------+

Where the VMB_i (variable meta data block) hold meta data related to the data chunk stored in VDB_ij (variable chunk). The number of data chunks (e.g. k and l in the scetch), generally may differ. We refer to the set VMB_i, VC_i1, ..., VC_ik as VCB_i (variable chunk block).

The VMB_i have the following sub structure:

   |<-------------- VMB_i ------------->|
   #                                    #
   +-------++---------+      +----------+
   |       ||         |      |          |
   | BMD_i || VMD_i1  | ---- | VMD_ij   |
   |       ||         |      |          |
   +-------++---------+      +----------+

Where the BMD_i (block meta data) have the following structure:

   BMD_i {
       numvars          // Number of variable chunks in data block 
       dbsize           // Size of entire block VCB_i (meta + actual data)
   }

The VMD_ij have the following structure:

   VMD_ij {
       id               // Id of protected variable the data chunk belongs to
       idx              // Index of element in FTI_Data corresponding to protected variable with id='id'
       containerid      // Id of container variable chunk is stored in
       hascontent       // Boolean value indicating if container holds data or not
       dptr             // Position of chunk in runtime-data (FTI_Data[idx].ptr + dptr)
       fptr             // Position of chunk in file
       chunksize        // Size of chunk stored in container
       containersize    // Total space in container
       hash             // Hash of 'VC_ij'
   }