Repairing A File System - Red Hat ENTERPRISE LINUX 5 - GLOBAL FILE SYSTEM 2 Manual

gfs2_tool unfreeze /mygfs2

3.11. Repairing a File System

When nodes fail with the file system mounted, file system journaling allows fast recovery. However,
if a storage device loses power or is physically disconnected, file system corruption may occur.
(Journaling cannot be used to recover from storage subsystem failures.) When that type of corruption
occurs, you can recover the GFS2 file system by using the fsck.gfs2 command.
Warning
The fsck.gfs2 command must be run only on a file system that is unmounted from all
nodes.
Note
If you have previous experience using the gfs_fsck command on GFS file systems, note
that the fsck.gfs2 command differs from some earlier releases of gfs_fsck in the in
the following ways:
• Pressing Ctrl+C while running the fsck.gfs2 interrupts processing and displays a
prompt asking whether you would like to abort the command, skip the rest of the current
pass, or continue processing.
• You can increase the level of verbosity by using the -v flag. Adding a second -v flag
increases the level again.
• You can decrease the level of verbosity by using the -q flag. Adding a second -q flag
decreases the level again.
• The -n option opens a file system as read-only and answers no to any queries
automatically. The option provides a way of trying the command to reveal errors without
actually allowing the fsck.gfs2 command to take effect.
Refer to the fsck.gfs2 man page for additional information about other command
options.
Running the fsck.gfs2 command requires system memory above and beyond the memory used
for the operating system and kernel. Each block of memory in the GFS2 file system itself requires
approximately five bits of additional memory, or 5/8 of a byte. So to estimate how many bytes of
memory you will need to run the fsck.gfs2 command on your file system, determine how many
blocks the file system contains and multiply that number by 5/8.
For example, to determine approximately how much memory is required to run the fsck.gfs2
command on a GFS2 file system that is 16TB with a block size of 4K, first determine how many blocks
of memory the file system contains by dividing 16Tb by 4K:
17592186044416 / 4096 = 4294967296
Repairing a File System
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