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Cluster Logical Volume And Global File system.

1)LOCK MANAGEMENT: it will make sure one particular file is written by only one particular process at any instances of time.
Another Words: if any of the process open a file in write mode
no other process will able to write it at the time.
PARTICLE EXAMPLE: if same file open by the two process,when second process open file you will get warning message like below in read mode.

GFS             > Uses Lock Manager > Synchronize access to the file system.
CLVM          > Uses Lock Manager > Synchronize update to the LVM and volume group.
Rgmanager > Uses Lock Manager > Synchronize the service states.
Synchronized access to the shared resources.
Advantage: Avoid inconsistency.

CLVM & CMAN will interact background for sharing cluster resources & information.
Comparison Between LVM, High Availability LVM  , Cluster LVM

LVM -> Available only on single node

LVM in Clustering failover mode. Active Passive mode. LVM -> Available across the multiple cluster nodes.
No other service need to be run. No other service need to be run.
Clvmd -> Service should run across all the cluster nodes. It will distribute the metadata in the cluster and provide the same logical volume to all the cluster nodes.
NOTE: All the functionality like create/reduce similar to the LVM except clvmd service.
(File Based Locking)
(File Based Locking)
(Cluster Locking)

Comparison Between GFS and Lustre.

GFS(Global File system) LUSTRE
1)Shared File system Distributed File system
2) Maintain the High availability(or) Load Balancing more than two nodes. High Performance Computing Environment.
3) Allow all nodes to have concurrent access to the same shared block storage.(no client or server models,All node in GFS cluster function as peers). Have server/client Communication setup in the cluster.

Global File System Installation

Step By Step CLVM Configuration
1)[root@node11 ~]# /etc/init.d/clvmd start
Starting clvmd:
Activating VG(s): 0 logical volume(s) in volume group "vgcluster" now active
2 logical volume(s) in volume group "vgcluster3" now active
[ OK ]
2)[root@node11 ~]# pvcreate /dev/mapper/1IET_00020001p1
Physical volume "/dev/mapper/1IET_00020001p1" successfully created
3)[root@node11 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/mapper/1IET_00020001p1 lvm2 a-- 2.00g 2.00g
Whatever create physical it will automatically reflect in the node10 (Remaining Cluster node) also.
How it is happens because of the clvmd service.
4)[root@node11 ~]# vgcreate vgcluster /dev/mapper/1IET_00020001p1
Clustered volume group "vgcluster" successfully created
5)[root@node11 ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vgcluster 1 0 0 wz--nc 2.00g 2.00g
6)[root@node11 ~]# lvcreate -L +500M -n lvcluster vgcluster
Logical volume "lvcluster" create
7)[root@node10 ~]# mkfs.gfs2 -j 2 -p lock_dlm -t MY_CLUSTER2:mygfs2 /dev/vgcluster/lvcluster-gfs 
-j <Journling>
-p  <name of the locking protocol>
This will destroy any data on /dev/vgcluster/lvcluster-gfs.
It appears to contain: symbolic link to `../dm-4'
Are you sure you want to proceed? [y/n] y
Device: /dev/vgcluster/lvcluster-gfs
Blocksize: 4096
Device Size 0.49 GB (128000 blocks)
Filesystem Size: 0.49 GB (127997 blocks)
Journals: 2
Resource Groups: 2
Locking Protocol: "lock_dlm"
Lock Table: "MY_CLUSTER2:mygfs2"
UUID: afd06add-4c31-640e-488e-db057d2b42e4

Solution And Error Message
# mkfs.gfs2 -j 2 -p lock_dlm -t MY_CLUSTER2:mygfs2 /dev/vgcluster/lvcluster-gfs 
 This will destroy any data on /dev/vgcluster/lvcluster-gfs.
It appears to contain: symbolic link to `../dm-5'
Are you sure you want to proceed? [y/n] y
Not enough space available on device
Solution: While Creating the lvm Give around 500MB then the problem got solved.

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