Summary: This article is a step-by-step guide for deploying a two-node IBM® General Parallel File System (IBM GPFS™) V3.5 cluster on IBM AIX® 7.1.
Figure 1. Visual representation of the cluster configuration
GPFS offers data tiering, replication, and many other advanced features. The configuration can be as simple or complex as you want.
In this article, each partition was built with AIX version 7.1, Technology Level 2, Service Pack 1:
Figure 2. Deployment diagram
The following attributes, shown in the table below, were changed for each hdisk, using thechdev command.
Thelsattr command can be used to verify that each attribute is set to the correct value:
You can refer to the step-by-step guide for configuring SSH keys on AIX:
You can confirm that the nodes can communicate with each other (unhindered) usingSSH with the following commands on each node:
Copy the node file to all nodes in the cluster.
Add the following entry to the root users .kshrc file. This will allow the root user to execute commands on all nodes in the GPFS cluster using thedsh or mmdsh commands.
mm commands are available to the system administrator. Add the following entry to the root user's .kshrc file.
We will install GPFS version 3.5 (base-level file sets) and then apply the latest updates to bring the level up to 3.5.0.10. There are only three file sets to install. You can use System Management Interface Tool (SMIT) or theinstallp command to install the software.
You can verify that the base-level GPFS file sets are installed by using thelslpp command:
installp ) to update the file sets to the latest level. The lslpp command can be used to verify that the GPFS file sets have been updated.
mmcrcluster command.* The GPFS cluster name is GPFS_CLUSTER1. The primary node (orNSD server; discussed in the next section) is aixlpar1p and the secondary node is aixlpar2p. We have specified that ssh andscp will be used for cluster communication and administration.
*Note: To ensure that GPFS daemon communication occurs over the private GPFS network, during cluster creation, we specified the GPFS daemon node names (that is, host names ending with p). There are two types of communication to consider in a GPFS cluster, administrative commands and daemon communication. Administrative commands use remote shell (ssh , rsh , or other) and socket-based communications. It is considered as a best practice to ensure that all GPFS daemon communication is performed over a private network. Refer to the GPFS developerWorks wiki for further information and discussion on GPFS network configuration considerations and practices.
To use a separate network for administration command communication, you can change the "Admin node name" using the mmchnode command. In this example, the separate network address is designated by "a" (for Administration) at the end of the node name, aixlpar1a for example.
mmcrcluster command warned us that not all nodes have the appropriate GPFS license designation. We use the mmchlicense command to assign a GPFS server license to both the nodes in the cluster.
mmlscluster command can be used to display cluster information.
mmdsh command to verify that the SSH communication is working as expected on all GPFS nodes. This runs a command on all the nodes in the cluster. If there is an SSH configuration problem, this command highlights the issues.
A shared disk cluster is the most basic environment. In this configuration, the storage is directly attached to all the systems in the cluster. The direct connection means that each shared block device is available concurrently to all of the nodes in the GPFS cluster. Direct access means that the storage is accessible using a Small Computer System Interface (SCSI) or other block-level protocol using a SAN.
The following figure illustrates a GPFS cluster where all nodes are connected to a common Fibre Channel SAN and storage device. The nodes are connected to the storage using the SAN and to each other using a local area network (LAN). Data used by applications running on the GPFS nodes flows over the SAN, and GPFS control information flows among the GPFS instances in the cluster over the LAN. This configuration is optimal when all nodes in the cluster need the highest performance access to the data.
Figure 3. Overview diagram of the GPFS cluster
Themmcrnsd command is used to create NSD devices for GPFS. First, we create a text file that contains a list of each of the hdisk names, their GPFS designation (data, metadata, both*), and the NSD name.
*Note: Refer to the GPFS Concepts, Planning, and Installation document for guidance on selecting NSD device usage types.
Then, run themmcrnsd command to create the NSD devices.
lspv command now shows the NSD name associated with each AIX hdisk.
mmlsnsd command displays information for each NSD, in particular which GPFS file system is associated with each device. At this point, we have not created a GPFS file system. So each disk is currently free. You'll notice that under NSD servers each device is shown as directly attached. This is expected for SAN-attached disks.
mmcrfs command is used to create the file systems. We have chosen to create two file systems; /gpfs and /gpfs1. The /gpfs (gpfs0) file system will be configured with a GPFS block size of 256K (the default) and /gpfs1 (gpfs1) with a block size of 1M*. Both file systems are configured for replication (-M2 –R2). The /tmp/cg/gpfs-disk.txt file is specified for /gpfs and /tmp/cg/gpfs1-disk.txt for /gpfs1. These files specify which NSD devices are used for each file system during creation.
*Note: Choose your block size carefully. It is not possible to change this value after the GPFS device has been created.
mmlsnsd command displays the NSD configuration per file system. NSD devices 1 to 3 are assigned to the gpfs0 device and devices 4 to 6 are assigned to gpfs1.
mmdsh command can be used here to quickly check the file system status on all the nodes.
mmdf command can be used.
In this example, we chose three (out of six) NSD devices as tiebreaker disks. We stopped GPFS on all nodes and configured the cluster accordingly.
mmfsd64 and runmmfs ).
mmgetstate command to view the status of the GPFS daemons on all the nodes in the cluster.
Overview
The purpose of this article is to provide a step-by-step guide for installing and configuring a simple two-node GPFS cluster on AIX. The following diagram provides a visual representation of the cluster configuration.Figure 1. Visual representation of the cluster configuration
GPFS
GPFS provides a true "shared file system" capability, with excellent performance and scalability. GPFS allows concurrent access for a group of computers to a common set of file data over a common storage area network (SAN) infrastructure, a network, or a mix of connection types. GPFS provides storage management, information lifecycle management tools, and centralized administration and allows for shared access to file systems from remote GPFS clusters providing a global namespace.
GPFS offers data tiering, replication, and many other advanced features. The configuration can be as simple or complex as you want.
Preparing the AIX environment for GPFS
We'll assume that you have already purchased the necessary licenses and software for GPFS. With a copy of the GPFS software available, copy the GPFS file sets to each of the AIX nodes on which you need to run GPFS.In this article, each partition was built with AIX version 7.1, Technology Level 2, Service Pack 1:
# oslevel -s 7100-02-01-1245Each AIX system is configured with seven SAN disks. One disk is used for the AIX operating system (rootvg) and the remaining six disks are used by GPFS.
# lspv hdisk0 00c334b6af00e77b rootvg active hdisk1 none none hdisk2 none none hdisk3 none none hdisk4 none none hdisk5 none none hdisk6 none noneThe SAN disks (to be used with GPFS) are assigned to both nodes (that is, they are shared between both partitions). Both AIX partitions are configured with virtual Fibre Channel adapters and access their shared storage through the SAN, as shown in the following figure.
Figure 2. Deployment diagram
The following attributes, shown in the table below, were changed for each hdisk, using the
| AIX device name | Size in GB | AIX disk device type | Algorithm | queue_depth | reserve_policy |
| hdisk0 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
| hdisk1 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
| hdisk2 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
| hdisk3 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
| hdisk4 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
| hdisk5 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
| hdisk6 | 50 | Hitachi MPIO Disk VSP | round_robin | 32 | no_reserve |
The
# lsattr -El hdisk6 –a queue_depth –q algorithm –a reserve_policy algorithm round_robin Algorithm True queue_depth 32 Queue DEPTH True reserve_policy no_reserve Reserve Policy True
The next step is to configure Secure Shell (SSH) so that both nodes can communicate with each other. When building a GPFS cluster, you must ensure that the nodes in the cluster have SSH configured correctly so that they do not require password authentication. This requires the configuration of Rivest-Shamir-Adleman algorithm (RSA) key pairs for the root users SSH configuration. This configuration needs to be configured in both directions, to all nodes in the GPFS cluster.
The mm commands in GPFS require authentication in order for them to work. If the keys are not configured correctly, the commands will prompt for the root password each time and the GPFS cluster might fail. A good way to test this is to ensure that the ssh command can work unhindered by a request for the roots password.
You can refer to the step-by-step guide for configuring SSH keys on AIX:
You can confirm that the nodes can communicate with each other (unhindered) using
aixlpar1# ssh aixlpar1a date aixlpar1# ssh aixlpar2a date aixlpar2# ssh aixlpar2a date aixlpar2# ssh aixlpar1a dateWith SSH working, configure the WCOLL (Working Collective) environment variable for the root user. For example, create a text file that lists each of the nodes, one per line:
# vi /usr/local/etc/gfps-nodes.list aixlpar1a aixlpar2a
Copy the node file to all nodes in the cluster.
Add the following entry to the root users .kshrc file. This will allow the root user to execute commands on all nodes in the GPFS cluster using the
export WCOLL=/usr/local/etc/gfps-nodes.listThe root users PATH should be modified to ensure that all GPFS
export PATH=$PATH:/usr/sbin/acct:/usr/lpp/mmfs/binThe /etc/hosts file should be consistent across all nodes in the GPFS cluster. Each IP address for each node must be added to/etc/hosts on each cluster node. This is recommended, even when Domain Name System (DNS) is configured on each node. For example:
# GPFS_CLUSTER1 Cluster - Test # # GPFS Admin network - en0 10.1.5.110 aixlpar1a aixlpar1 10.1.5.120 aixlpar2a aixlpar2 # # GPFS Daemon - Private Network – en1 10.1.7.110 aixlpar1p 10.1.7.120 aixlpar2p
Installing GPFS on AIX
Now that the AIX environment is configured, the next step is to install the GPFS software on each node. This is a very straight forward process.We will install GPFS version 3.5 (base-level file sets) and then apply the latest updates to bring the level up to 3.5.0.10. There are only three file sets to install. You can use System Management Interface Tool (SMIT) or the
aixlpar1 : /tmp/cg/GPFS/gpfs35_aix # inutoc . aixlpar1 : /tmp/cg/GPFS/gpfs35_aix # ls -ltr total 123024 -rw-r--r-- 1 root system 175104 Jun 7 2012 gpfs.msg.en_US -rw-r--r-- 1 root system 868352 Jun 7 2012 gpfs.docs.data -rw-r--r-- 1 root system 61939712 Jun 7 2012 gpfs.base -rw-r--r-- 1 root system 3549 Apr 26 16:37 .toc aixlpar1 : /tmp/cg/GPFS/gpfs35_aix # install –Y –d . ALLRepeat this operation on the second node.
You can verify that the base-level GPFS file sets are installed by using the
# lslpp -l | grep -i gpfs gpfs.base 3.5.0.0 COMMITTED GPFS File Manager gpfs.msg.en_US 3.5.0.0 COMMITTED GPFS Server Messages - U.S. gpfs.base 3.5.0.0 COMMITTED GPFS File Manager gpfs.docs.data 3.5.0.0 COMMITTED GPFS Server Manpages andThe latest GPFS updates are installed next. Again, you can use SMIT (or
aixlpar1 : /tmp/cg/gpfs_fixes_3510 # inutoc .
aixlpar1 : /tmp/cg/gpfs_fixes_3510 # ls -ltr
total 580864
-rw-r--r-- 1 30007 bin 910336 Feb 9 00:10 U858102.gpfs.docs.data.bff
-rw-r--r-- 1 30007 bin 47887360 May 8 08:48 U859646.gpfs.base.bff
-rw-r--r-- 1 30007 bin 99655680 May 8 08:48 U859647.gpfs.gnr.bff
-rw-r--r-- 1 30007 bin 193536 May 8 08:48 U859648.gpfs.msg.en_US.bff
-rw-r--r-- 1 root system 4591 May 10 05:15 changelog
-rw-r--r-- 1 root system 3640 May 10 05:42 README
-rw-r----- 1 root system 55931 May 15 10:23 GPFS-3.5.0.10-power-AIX.readme.html
-rw-r----- 1 root system 148664320 May 15 10:28 GPFS-3.5.0.10-power-AIX.tar
-rw-r--r-- 1 root system 8946 May 15 14:48 .toc
aixlpar1 : /tmp/cg/gpfs_fixes_3510 # smitty update_all
COMMAND STATUS
Command: OK stdout: yes stderr: no
Before command completion, additional instructions may appear below.
[MORE...59]
Finished processing all filesets. (Total time: 18 secs).
+-----------------------------------------------------------------------------+
Pre-commit Verification...
+-----------------------------------------------------------------------------+
Verifying requisites...done
Results...
SUCCESSES
---------
Filesets listed in this section passed pre-commit verification
and will be committed.
Selected Filesets
-----------------
gpfs.base 3.5.0.10 # GPFS File Manager
gpfs.msg.en_US 3.5.0.9 # GPFS Server Messages - U.S. ...
<< End of Success Section >>
+-----------------------------------------------------------------------------+
Committing Software...
+-----------------------------------------------------------------------------+
installp: COMMITTING software for:
gpfs.base 3.5.0.10
Filesets processed: 1 of 2 (Total time: 18 secs).
installp: COMMITTING software for:
gpfs.msg.en_US 3.5.0.9
Finished processing all filesets. (Total time: 18 secs).
+-----------------------------------------------------------------------------+
Summaries:
+-----------------------------------------------------------------------------+
Installation Summary
--------------------
Name Level Part Event Result
-------------------------------------------------------------------------------
gpfs.msg.en_US 3.5.0.9 USR APPLY SUCCESS
gpfs.base 3.5.0.10 USR APPLY SUCCESS
gpfs.base 3.5.0.10 ROOT APPLY SUCCESS
gpfs.base 3.5.0.10 USR COMMIT SUCCESS
gpfs.base 3.5.0.10 ROOT COMMIT SUCCESS
gpfs.msg.en_US 3.5.0.9 USR COMMIT SUCCESS
aixlpar1 : /tmp/cg/gpfs_fixes_3510 # lslpp -l gpfs\*
Fileset Level State Description
----------------------------------------------------------------------------
Path: /usr/lib/objrepos
gpfs.base 3.5.0.10 COMMITTED GPFS File Manager
gpfs.msg.en_US 3.5.0.9 COMMITTED GPFS Server Messages - U.S.
English
Path: /etc/objrepos
gpfs.base 3.5.0.10 COMMITTED GPFS File Manager
Path: /usr/share/lib/objrepos
gpfs.docs.data 3.5.0.3 COMMITTED GPFS Server Manpages and
Documentation
Repeat the update on the second node.Configuring the GPFS cluster
Now that GPFS is installed, we can create a cluster across both AIX systems. First, we create a text file that contains a list of each of the nodes and their GPFS description and purpose. We have chosen to configure each node as a GPFS quorum manager. Each node is a GPFS server. If you are unsure of how many quorum managers and GPFS servers are required in your environment, refer to the GPFS Concepts, Planning, and Installation document for guidance.aixlpar1 : /tmp/cg # cat gpfs-nodes.txt aixlpar2p:quorum-manager: aixlpar1p:quorum-manager:The cluster is created using the
aixlpar1 : /tmp/cg # mmcrcluster –C GPFS_CLUSTER1 -N /tmp/cg/gpfs-nodes.txt -p aixlpar1p -s aixlpar2p -r /usr/bin/ssh -R /usr/bin/scp Mon Apr 29 12:01:21 EET 2013: mmcrcluster: Processing node aixlpar2 Mon Apr 29 12:01:24 EET 2013: mmcrcluster: Processing node aixlpar1 mmcrcluster: Command successfully completed mmcrcluster: Warning: Not all nodes have proper GPFS license designations. Use the mmchlicense command to designate licenses as needed. mmcrcluster: Propagating the cluster configuration data to all affected nodes. This is an asynchronous process.
*Note: To ensure that GPFS daemon communication occurs over the private GPFS network, during cluster creation, we specified the GPFS daemon node names (that is, host names ending with p). There are two types of communication to consider in a GPFS cluster, administrative commands and daemon communication. Administrative commands use remote shell (
To use a separate network for administration command communication, you can change the "Admin node name" using the
# mmchnode -admin-interface=aixlpar1p -N aixlpar1a # mmchnode -admin-interface=aixlpar2p -N aixlpar2aThe
aixlpar1 : / # mmchlicense server --accept -N aixlpar1a,aixlpar2a The following nodes will be designated as possessing GPFS server licenses: aixlpar2a aixlpar1a mmchlicense: Command successfully completed mmchlicense: Propagating the cluster configuration data to all affected nodes. This is an asynchronous process.The cluster is now configured. The
# mmlscluster GPFS cluster information ======================== GPFS cluster name: GPFS_CLUSTER1.aixlpar1p GPFS cluster id: 8831612751005471855 GPFS UID domain: GPFS_CLUSTER.aixlpar1p Remote shell command: /usr/bin/ssh Remote file copy command: /usr/bin/scp GPFS cluster configuration servers: ----------------------------------- Primary server: aixlpar1p Secondary server: aixlpar2p Node Daemon node name IP address Admin node name Designation ---------------------------------------------------------------------- 1 aixlpar2p 10.1.7.120 aixlpar2a quorum-manager 2 aixlpar1p 10.1.7.110 aixlpar1a quorum-managerAt this point, you can use the
aixlpar1 : / # mmdsh date aixlpar1: Mon Apr 29 12:05:47 EET 2013 aixlpar2: Mon Apr 29 12:05:47 EET 2013 aixlpar2 : / # mmdsh date aixlpar1: Mon Apr 29 12:06:41 EET 2013 aixlpar2: Mon Apr 29 12:06:41 EET 2013
GPFS provides a block-level interface over TCP/IP networks called the Network Shared Disk (NSD) protocol. Whether using the NSD protocol or a direct attachment to the SAN, the mounted file system looks the same to the users and application (GPFS transparently handles I/O requests).
A shared disk cluster is the most basic environment. In this configuration, the storage is directly attached to all the systems in the cluster. The direct connection means that each shared block device is available concurrently to all of the nodes in the GPFS cluster. Direct access means that the storage is accessible using a Small Computer System Interface (SCSI) or other block-level protocol using a SAN.
The following figure illustrates a GPFS cluster where all nodes are connected to a common Fibre Channel SAN and storage device. The nodes are connected to the storage using the SAN and to each other using a local area network (LAN). Data used by applications running on the GPFS nodes flows over the SAN, and GPFS control information flows among the GPFS instances in the cluster over the LAN. This configuration is optimal when all nodes in the cluster need the highest performance access to the data.
Figure 3. Overview diagram of the GPFS cluster
The
hdisk1:::dataAndMetadata::nsd01:: hdisk2:::dataAndMetadata::nsd02:: hdisk3:::dataAndMetadata::nsd03:: hdisk4:::dataAndMetadata::nsd04:: hdisk5:::dataAndMetadata::nsd05:: hdisk6:::dataAndMetadata::nsd06::
Note:Here you can specify the nodes in second field , if you want to limit the nsd disks to be created on specific nodes.Like hdisk1:aixlpar1p,aixlpar3p::dataAndMetadata::nsd01::
*Note: Refer to the GPFS Concepts, Planning, and Installation document for guidance on selecting NSD device usage types.
Then, run the
# mmcrnsd -F /tmp/cg/gpfs-disks.txt mmcrnsd: Processing disk hdisk1 mmcrnsd: Processing disk hdisk2 mmcrnsd: Processing disk hdisk3 mmcrnsd: Processing disk hdisk4 mmcrnsd: Processing disk hdisk5 mmcrnsd: Processing disk hdisk6 mmcrnsd: Propagating the cluster configuration data to all affected nodes. This is an asynchronous process.The
# lspv hdisk0 00c334b6af00e77b rootvg active hdisk1 none nsd01 hdisk2 none nsd02 hdisk3 none nsd03 hdisk4 none nsd04 hdisk5 none nsd05 hdisk6 none nsd06The
# mmlsnsd File system Disk name NSD servers --------------------------------------------------------------------------- (free disk) nsd01 (directly attached) (free disk) nsd02 (directly attached) (free disk) nsd03 (directly attached) (free disk) nsd04 (directly attached) (free disk) nsd05 (directly attached) (free disk) nsd06 (directly attached)
GPFS file system configuration
Next, the GPFS file systems can be configured. The*Note: Choose your block size carefully. It is not possible to change this value after the GPFS device has been created.
# cat /tmp/cg/gpfs-disk.txt nsd01:::dataAndMetadata:-1::system nsd02:::dataAndMetadata:-1::system nsd03:::dataAndMetadata:-1::system # cat /tmp/cg/gpfs1-disk.txt nsd04:::dataAndMetadata:-1::system nsd05:::dataAndMetadata:-1::system nsd06:::dataAndMetadata:-1::system # mmcrfs /gpfs gpfs0 -F/tmp/cg/gpfs-disks.txt -M2 -R 2 # mmcrfs /gpfs1 gpfs1 -F/tmp/cg/gpfs1-disks.txt -M2 -R 2 –B 1MThe
# mmlsnsd File system Disk name NSD servers --------------------------------------------------------------------------- gpfs0 nsd01 (directly attached) gpfs0 nsd02 (directly attached) gpfs0 nsd03 (directly attached) gpfs1 nsd04 (directly attached) gpfs1 nsd05 (directly attached) gpfs1 nsd06 (directly attached)Both GPFS file systems are now available on both nodes.
aixlpar1 : / # df -g Filesystem GB blocks Free %Used Iused %Iused Mounted on /dev/hd4 1.00 0.89 12% 5211 3% / /dev/hd2 3.31 0.96 71% 53415 18% /usr /dev/hd9var 2.00 1.70 16% 5831 2% /var /dev/hd3 2.00 1.36 33% 177 1% /tmp /dev/hd1 2.00 2.00 1% 219 1% /home /proc - - - - - /proc /dev/hd10opt 1.00 0.79 21% 3693 2% /opt /dev/local 1.00 0.97 3% 333 1% /usr/local /dev/loglv 1.00 1.00 1% 54 1% /var/log /dev/tsmlog 1.00 1.00 1% 7 1% /var/tsm/log /dev/hd11admin 0.12 0.12 1% 13 1% /admin /dev/optIBMlv 2.00 1.99 1% 17 1% /opt/IBM /dev/gpfs1 150.00 147.69 2% 4041 3% /gpfs1 /dev/gpfs0 150.00 147.81 2% 4041 7% /gpfsThe
aixlpar1 : / # mmdsh df -g | grep gpfs aixlpar2: /dev/gpfs0 150.00 147.81 2% 4041 7% /gpfs aixlpar2: /dev/gpfs1 150.00 147.69 2% 4041 3% /gpfs1 aixlpar1: /dev/gpfs1 150.00 147.69 2% 4041 3% /gpfs1 aixlpar1: /dev/gpfs0 150.00 147.81 2% 4041 7% /gpfsIf more detailed information is required, the
aixlpar1 : /gpfs # mmdf gpfs0 --block-size=auto
disk disk size failure holds holds free free
name group metadata data in full blocks in fragments
--------------- ------------- -------- -------- ----- -------------------- ------------
Disks in storage pool: system (Maximum disk size allowed is 422 GB)
nsd01 50G -1 yes yes 49.27G ( 99%) 872K ( 0%)
nsd02 50G -1 yes yes 49.27G ( 99%) 936K ( 0%)
nsd03 50G -1 yes yes 49.27G ( 99%) 696K ( 0%)
------------- -------------------- -------------------
(pool total) 150G 147.8G ( 99%) 2.445M ( 0%)
============= ==================== ===================
(total) 150G 147.8G ( 99%) 2.445M ( 0%)
Inode Information
-----------------
Number of used inodes: 4040
Number of free inodes: 62008
Number of allocated inodes: 66048
Maximum number of inodes: 66048
aixlpar1 : /gpfs # mmdf gpfs1 --block-size=auto
disk disk size failure holds holds free free
name group metadata data in full blocks in fragments
--------------- ------------- -------- -------- ----- --------------------
Disks in storage pool: system (Maximum disk size allowed is 784 GB)
nsd04 50G -1 yes yes 49.55G ( 99%) 1.938M ( 00%)
nsd05 50G -1 yes yes 49.56G ( 99%) 992K ( 0%)
nsd06 50G -1 yes yes 49.56G ( 99%) 1.906M ( 00%)
------------- -------------------- -------------------
(pool total) 150G 148.7G ( 99%) 4.812M ( 00%)
============= ==================== ===================
(total) 150G 148.7G ( 99%) 4.812M ( 00%)
Inode Information
-----------------
Number of used inodes: 4040
Number of free inodes: 155704
Number of allocated inodes: 159744
Maximum number of inodes: 159744
Node quorum with tiebreaker disks
Tiebreaker disks are recommended when you have a two-node cluster or you have a cluster where all of the nodes are SAN-attached to a common set of logical unit numbers (LUNs) and you want to continue to serve data with a single surviving node. Typically, tiebreaker disks are only used in two-node clusters. Tiebreaker disks are not special NSDs; you can use any NSD as a tiebreaker disk.In this example, we chose three (out of six) NSD devices as tiebreaker disks. We stopped GPFS on all nodes and configured the cluster accordingly.
# mmshutdown -N # mmchconfig tiebreakerDisks="nsd01;nsd03;nsd05" # mmstartup -a
Cluster daemon status
There are two GPFS daemons (processes) that remain active while GPFS is active (# ps -ef | grep mmfs root 4784176 5505220 0 May 20 - 0:27 /usr/lpp/mmfs/bin/aix64/mmfsd64 root 5505220 1 0 May 20 - 0:00 /usr/lpp/mmfs/bin/mmksh /usr/lpp/mmfs/bin/runmmfsYou can use the
# mmgetstate -aLs
Node number Node name Quorum Nodes up Total nodes GPFS state Remarks
------------------------------------------------------------------------------------
1 aixlpar2a 1* 2 2 active quorum node
2 aixlpar1a 1* 2 2 active quorum node
Summary information
---------------------
Number of nodes defined in the cluster: 2
Number of local nodes active in the cluster: 2
Number of remote nodes joined in this cluster: 0
Number of quorum nodes defined in the cluster: 2
Number of quorum nodes active in the cluster: 2
Quorum = 1*, Quorum achieved
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