The GFS Shared File System uses extent based area management. If a file has many extents, some of extents are stored as indirect blocks in V-data area.
In this case, an allocation of new blocks could induce a rebuilding of indirect block. It would consume many V-data area. To prevent V-data starvation, GFS prevents an allocation of new block when V-data area usage exceeds 80%. In this case, a system-call (e.g. write(2)) which attempts to allocate a new block fails with ENOSPC.
Deleting unused files or directories or moving them into other file systems helps you to reduce V-data area usage.
See
For information on how to check usage of V-data area, see B.1.1 sfcdf(8) Display the GFS Shared File System use status and configuration information.
