diff options
Diffstat (limited to 'drivers/staging/lustre/lustre/fld/fld_internal.h')
| -rw-r--r-- | drivers/staging/lustre/lustre/fld/fld_internal.h | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/drivers/staging/lustre/lustre/fld/fld_internal.h b/drivers/staging/lustre/lustre/fld/fld_internal.h index f0efe5b9fbec..08eaec735d6f 100644 --- a/drivers/staging/lustre/lustre/fld/fld_internal.h +++ b/drivers/staging/lustre/lustre/fld/fld_internal.h @@ -31,6 +31,25 @@ * * lustre/fld/fld_internal.h * + * Subsystem Description: + * FLD is FID Location Database, which stores where (IE, on which MDT) + * FIDs are located. + * The database is basically a record file, each record consists of a FID + * sequence range, MDT/OST index, and flags. The FLD for the whole FS + * is only stored on the sequence controller(MDT0) right now, but each target + * also has its local FLD, which only stores the local sequence. + * + * The FLD subsystem usually has two tasks: + * 1. maintain the database, i.e. when the sequence controller allocates + * new sequence ranges to some nodes, it will call the FLD API to insert the + * location information <sequence_range, node_index> in FLDB. + * + * 2. Handle requests from other nodes, i.e. if client needs to know where + * the FID is located, if it can not find the information in the local cache, + * it will send a FLD lookup RPC to the FLD service, and the FLD service will + * look up the FLDB entry and return the location information to client. + * + * * Author: Yury Umanets <umka@clusterfs.com> * Author: Tom WangDi <wangdi@clusterfs.com> */ |