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

Chapter 3. Managing GFS

3.14. 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 GFS file system by using the gfs_fsck command.
Warning
The gfs_fsck command must be run only on a file system that is unmounted from all
nodes.
Note
The gfs_fsck command has changed from previous releases of Red Hat GFS in the
following ways:
• Pressing Ctrl+C while running the gfs_fsck 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 gfs_fsck command to take effect.
Refer to the gfs_fsck man page, gfs_fsck(8), for additional information about other
command options.
Running the gfs_fsck command requires system memory above and beyond the memory used for
the operating system and kernel. Each block of memory in the file system itself requires approximately
one byte of additional memory. So to estimate the amount of memory you will need to run the
gfs_fsck command on your file system, divide the file system size (in bytes) by the block size.
For example, for a GFS file system that is 16TB with a block size of 4K, divide 16TB by 4K:
17592186044416 / 4096 = 4294967296
This file system requires approximately 4GB of free memory to run the gfs_fsck command. Note
that if the block size was 1K, running the gfs_fsck command would require four times the memory,
or 16GB.
Usage
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