What is the minimum size of the Quorum Disk?
The minimum size of the block device is 10 Megabytes.

What is the order in which you will start the Red Hat Cluster services?
In Red Hat 4
service ccsd start
service cman start
service fenced start
service clvmd start (If CLVM has been used to create clustered volumes)
service gfs start
service rgmanager start

In RedHat 5
service cman start
service clvmd start
service gfs start
service rgmanager start

In Red Hat 6
service cman start
service clvmd start
service gfs2 start
service rgmanager start

What is the order to stop the Red Hat Cluster services?
In Red Hat 4
service rgmanager stop
service gfs stop
service clvmd stop
service fenced stop
service cman stop
service ccsd stop


In Red Hat 5
service rgmanager stop
service gfs stop
service clvmd stop
service cman stop

In Red Hat 6
service rgmanager stop
service gfs2 stop
service clvmd stop
service cman stop



What are the performance enhancements in GFS2 as compared to GFS?
  • Better performance for heavy usage in a single directory
  • Faster synchronous I/O operations
  • Faster cached reads (no locking overhead)
  • Faster direct I/O with preallocated files (provided I/O size is reasonably large, such as 4M blocks)
  • Faster I/O operations in general
  • Faster Execution of the df command, because of faster statfs calls
  • Improved atime mode to reduce the number of write I/O operations generated by atime when compared with GFS
  • GFS2 supports the following features.
  • extended file attributes (xattr)
  • the lsattr() and chattr() attribute settings via standard ioctl() calls
  • nanosecond timestamps
  • GFS2 uses less kernel memory.
  • GFS2 requires no metadata generation numbers.
  • Allocating GFS2 metadata does not require reads. Copies of metadata blocks in multiple journals are managed by revoking blocks from the journal before lock release.
  • GFS2 includes a much simpler log manager that knows nothing about unlinked inodes or quota changes.
  • The gfs2_grow and gfs2_jadd commands use locking to prevent multiple instances running at the same time.
  • The ACL code has been simplified for calls like creat() and mkdir().
  • Unlinked inodes, quota changes, and statfs changes are recovered without remounting the journal.

What is the maximum file system support size for GFS2?
  • GFS2 is based on 64 bit architecture, which can theoretically accommodate an 8 EB file system. 
  • However, the current supported maximum size of a GFS2 file system for 64-bit hardware is 100 TB. 
  • The current supported maximum size of a GFS2 file system for 32-bit hardware for Red Hat Enterprise Linux Release 5.3 and later is 16 TB. 
  • NOTE: It is better to have 10 1TB file systems than one 10TB file system.
What is the journaling filesystem?
  • A journaling filesystem is a filesystem that maintains a special file called a journal that is used to repair any inconsistencies that occur as the result of an improper shutdown of a computer.
  • In journaling file systems, every time GFS2 writes metadata, the metadata is committed to the journal before it is put into place. 
  • This ensures that if the system crashes or loses power, you will recover all of the metadata when the journal is automatically replayed at mount time.
  • GFS2 requires one journal for each node in the cluster that needs to mount the file system. For example, if you have a 16-node cluster but need to mount only the file system from two nodes, you need only two journals. If you need to mount from a third node, you can always add a journal with the gfs2_jadd command.