Using Global File System Checking

Describes how to use the gfsck command to check and repair file system errors.

About this task

You can use the gfsck (global file system check) command to perform a consistency check and repair operation on a volume or volume snapshot, including the following entities:

  • All cross-container links (for example, from file to filelet, or from table to tablets)
  • The tabletmap key range
  • The attributes of filelet (uid/gid/mode)

This command identifies the unreachable files, directories, and tables in the volume, and moves them to /lost+found to be repaired. It also identifies and fixes any unreachable DB inodes or dangling pointers to lost inodes.

The following table describes how the gfsck utility handles the objects based on the object size.

Table 1. gfsck Behavior for Various Object Sizes
Object Size How gfsck handles the Object
Tiny objects gfsck cannot re-construct tiny objects. gfsck cannot repair tiny objects.
Small objects gfsck can re-construct small objects. The re-constructed object file name has the same name as that of the original object file name.
Large objects gfsck can re-construct large objects. The re-constructed object file name differs from the original object file name. The filename of the re-constructed large object is large_objs_reconstruct_<fid>, where fid denotes the file ID of the original object.
Jumbo objects gfsck can re-construct jumbo objects. The re-constructed object file name differs from the original object file name. The filename of the re-constructed jumbo object is jumbo_objs_reconstruct_<fid>, where fid denotes file ID of the original object.

Procedure

  1. Take the affected storage pools offline by running the mrconfig sp offline command.
    For example: 
    /opt/mapr/server/mrconfig sp offline /dev/sdc
  2. Execute the fsck command on the storage pools or disks.
  3. Bring the storage pools back online by running the mrconfig sp online command.
    For example: 
    mrconfig sp online /dev/sdc
  4. Run the gfsck command on the affected volumes, or snapshots, with the appropriate options.
    If there are alarms, such as DataUnavailableAlarm or DataUnderReplicatedAlarm, do not run the gfsck command with the -r (--repair) option. Running the gfsck command with the -r (--repair) option, might result in data loss. If necessary, first run gfsck without the -r (--repair) option, and attempt to repair only after analyzing the command output.

    Troubleshooting

    While running the gfsck command with the --use-aux-memory option, you might encounter the following error in the gfsck.log file, when the auxDBTables directory is missing or has been removed accidentally:
    ERROR com.mapr.fs.globalfsck.GlobalFsck createLargeObjectTable [main]: AuxDb volume mapr.gfsck does not exist.

    Cause: The /var/mapr/auxDBTables directory is missing.

    Resolution:Restart the warden service. Restarting the warden service creates the auxDBTables directory in the /var/mapr directory.