This chapter introduces the TruCluster Server product and some basic cluster hardware configuration concepts.
The chapter discusses the following topics:
Overview of the TruCluster Server product (Section 1.1)
TruCluster Server memory requirements (Section 1.2)
TruCluster Server minimum disk requirements (Section 1.3)
Description of a generic two-node cluster with the minimum disk layout (Section 1.4)
How to grow a cluster to a no-single-point-of-failure (NSPOF) cluster (Section 1.5)
Overview of eight-member clusters (Section 1.6)
Overview of setting up the TruCluster Server hardware configuration (Section 1.7)
Subsequent chapters describe how to set up and maintain
TruCluster Server hardware configurations.
See the TruCluster Server
manual for information about software installation;
manual for detailed
information about setting up member systems; see the
Cluster Highly Available Applications
manual for detailed
information about setting up highly available applications.
1.1 TruCluster Server
TruCluster Server extends single-system management capabilities to clusters. It provides a clusterwide namespace for files and directories, including a single root file system that all cluster members share. It also offers a cluster alias for the Internet protocol suite (TCP/IP) so that a cluster appears as a single system to its network clients.
TruCluster Server preserves the availability and performance features found in the earlier TruCluster products:
Like the TruCluster Available Server Software and TruCluster Production Server products, TruCluster Server lets you deploy highly available applications that have no embedded knowledge that they are executing in a cluster. They can access their disk data from any member in the cluster.
Like the TruCluster Production Server Software product, TruCluster Server lets you run components of distributed applications in parallel, providing high availability while taking advantage of cluster-specific synchronization mechanisms and performance optimizations.
TruCluster Server augments the feature set of its predecessors by allowing
all cluster members access to all file systems and all storage in the
cluster, regardless of where they reside.
From the viewpoint of clients,
a TruCluster Server cluster appears to be a single system; from the viewpoint
of a system administrator, a TruCluster Server cluster is managed as if it
were a single system.
Because TruCluster Server has no built-in dependencies
on the architectures or protocols of its private cluster interconnect or
shared storage interconnect, you can more easily alter or expand your
cluster's hardware configuration as newer and faster technologies become
1.2 Memory Requirements
The base operation system sets a minimum requirement for the amount of
memory required to install Tru64 UNIX.
In a cluster, each member
must have at least 64 MB more than this minimum requirement.
example, if the base operating system requires 128 MB of memory, each
system used in a cluster must have at least 192 MB of memory.
1.3 Minimum Disk Requirements
This section provides an overview of the
minimum file system or disk requirements for a two-node
For more information on the amount of space required for
each required cluster file system, see the
1.3.1 Disks Needed for Installation
You need to allocate disks for the following uses:
One or more disks to hold the Tru64 UNIX operating system. The disks are either private disks on the system that will become the first cluster member, or disks on a shared bus that the system can access.
One or more disks on a shared bus to hold the
clusterwide root (
Advanced File System (AdvFS) file systems.
One disk per member, normally on a shared bus, to hold member boot partitions.
The following sections provide more information about these disks.
shows a generic two-member cluster
with the required file systems.
18.104.22.168 Tru64 UNIX Operating System Disk
The Tru64 UNIX operating system is installed using AdvFS file systems on one or more disks that are accessible to the system that will become the first cluster member. For example:
dsk0a root_domain#root dsk0g usr_domain#usr dsk0h var_domain#var
The operating system disk (Tru64 UNIX disk) cannot be used as a clusterwide disk, as a member boot disk, or as the quorum disk.
Because the Tru64 UNIX operating system will be available on the
first cluster member, in an emergency, after shutting down the
cluster, you have the option of booting the Tru64 UNIX operating
system and attempting to fix the problem.
manual for more information.
22.214.171.124 Clusterwide Disks
When you create a cluster, the installation scripts copy the
Tru64 UNIX root (
systems from the Tru64 UNIX disk to the disk or disks you specify.
We recommend that the disk or disks that you use for the clusterwide file systems be placed on a shared bus so that all cluster members have access to these disks.
During the installation, you supply the disk device names and partitions
that will contain the clusterwide
dsk3b cluster_root#root dsk4c cluster_usr#usr dsk3g cluster_var#var
file system cannot share the
domain, but must be a separate domain,
Each AdvFS file system must be a
separate partition; the partitions do not have to be on the same disk.
A disk containing a clusterwide file system cannot also be
used as the member boot disk or as the quorum disk.
126.96.36.199 Member Boot Disk
Each member has a boot disk.
A boot disk contains that member's
boot, swap, and cluster-status partitions.
is the boot disk for the first member and
the boot disk for the second member:
dsk1 first member's boot disk [pepicelli] dsk2 second member's boot disk [polishham]
The installation scripts reformat each member's boot disk to contain
three partitions: an
partition for that member's
/) file system, a
partition for swap,
partition for cluster status information.
file systems on
a member's boot disk.)
A member boot disk cannot contain one of the clusterwide
Also, a member boot disk cannot be
used as the quorum disk.
A member disk can contain more than the three
You can move the swap partition off the member
manual for more information.
188.8.131.52 Quorum Disk
The quorum disk allows greater availability for clusters
consisting of two members.
contains cluster status and quorum information.
manual for a discussion of how and
when to use a quorum disk.
The following restrictions apply to the use of a quorum disk:
A cluster can have only one quorum disk.
We recommend that the quorum disk be on a shared bus to which all cluster members are directly connected. If it is not, members that do not have a direct connection to the quorum disk may lose quorum before members that do have a direct connection to it.
The quorum disk must not contain any data.
command will overwrite existing data
when initializing the quorum disk.
The integrity of data (or file
system metadata) placed on the quorum disk from a running cluster is
not guaranteed across member failures.
Member boot disks and the disk holding the clusterwide root (/) cannot be used as quorum disks.
The quorum disk can be small. The cluster subsystems use only 1 MB of the disk.
A quorum disk can have either 1 vote or no votes. In general, we recommend that a quorum disk always be assigned a vote. You might assign an existing quorum disk no votes in certain testing or transitory configurations, such as a one-member cluster (in which a voting quorum disk introduces a single point of failure).
1.4 Generic Two-Node Cluster
This section describes a generic two-node cluster with the minimum disk layout of four disks. Additional disks may be needed for highly available applications. In this section, and the following sections, the type of peripheral component interconnect (PCI) SCSI bus adapter is not significant. Also, although an important consideration, SCSI bus cabling, including Y cables or trilink connectors, termination, the use of UltraSCSI hubs, and the use of Fibre Channel are not considered at this time.
Figure 1-1 shows a generic two-node cluster with the minimum number of disks.
Tru64 UNIX disk
Clusterwide root (
Member 1 boot disk
Member 2 boot disk
A minimum configuration cluster may have reduced availability due to
the lack of a quorum disk.
As shown, with only two-member systems,
both systems must be operational to achieve quorum and form a cluster.
If only one system is operational, it will loop, waiting for the second
system to boot before a cluster can be formed.
If one system crashes,
you lose the cluster.
Figure 1-1: Two-Node Cluster with Minimum Disk Configuration and No Quorum Disk
shows the same generic
two-node cluster as shown in
but with the addition of a quorum disk.
By adding a quorum disk, a
cluster may be formed if both systems are operational, or if either of
the systems and the quorum disk is operational.
This cluster has a
higher availability than the cluster shown in
manual for a discussion of how and when to use a quorum disk.
Figure 1-2: Generic Two-Node Cluster with Minimum Disk Configuration and Quorum Disk
1.5 Growing a Cluster from Minimum Storage to an NSPOF Cluster
The following sections take a progression of clusters from a cluster with minimum storage to a no-single-point-of-failure (NSPOF) cluster a cluster where one hardware failure will not interrupt the cluster operation:
The starting point is a cluster with minimum storage for highly available applications (Section 1.5.1).
By adding a second storage shelf, you have a cluster with more storage for applications, but the single SCSI bus is a single point of failure (Section 1.5.2).
Adding a second SCSI bus allows the use of LSM to mirror
the clusterwide root (
systems, the member system swap partitions, and the data disks.
However, because LSM cannot mirror the member system boot or quorum
disks, full redundancy is not achieved (Section 1.5.3).
Using a redundant array of independent disks (RAID) array controller in transparent failover mode allows the use of hardware RAID to mirror the disks. However, without a second SCSI bus, second cluster interconnect and redundant networks, this configuration is still not an NSPOF cluster (Section 1.5.4).
By using an HSZ80, HSG60, HSG80, or Enterprise
Virtual Array with multiple-bus
failover enabled, you can use two shared buses to access the
Hardware RAID is used to mirror the root
file systems, and the member system
boot disks, data disks, and quorum disk (if used).
cluster interconnect, redundant networks, and redundant power must also be
installed to achieve an NSPOF cluster (Section 1.5.5).
The figures in this section are generic drawings and do not show shared bus termination, cable names, and so forth.
1.5.1 Two-Node Clusters Using an UltraSCSI BA356 Storage Shelf and Minimum Disk Configurations
This section takes the generic illustrations of our cluster example one step further by depicting the required storage in storage shelves. The storage shelves can be BA350, BA356 (non-UltraSCSI), or UltraSCSI BA356s. The BA350 is the oldest model, and can only respond to SCSI IDs 0-6. The non-Ultra BA356 can respond to SCSI IDs 0-6 or 8-14. (See Section 3.2.) The UltraSCSI BA356 also responds to SCSI IDs 0-6 or 8-14, but also can operate at UltraSCSI speeds. (See Section 3.2.)
shows a TruCluster Server
configuration using an UltraSCSI BA356 storage unit.
personality module used in the UltraSCSI BA356 storage unit is a
differential-to-single-ended signal converter, and therefore accepts
Figure 1-3: Minimum Two-Node Cluster with UltraSCSI BA356 Storage Unit
The configuration shown in Figure 1-3 might represent a typical small or training configuration with TruCluster Server Version 5.1B required disks.
In this configuration, because of the TruCluster Server Version 5.1B disk requirements, only two disks are available for highly available applications.
Slot 6 in the UltraSCSI BA356 is not available because SCSI ID 6 is generally used for a member system SCSI adapter. However, this slot can be used for a second power supply to provide fully redundant power to the storage shelf.
With the use of the cluster file system (see the
manual for a discussion of the cluster file system),
the clusterwide root (
can be physically placed on a private bus of either of the member
But, if that member system is not available, the other
member systems do not have access to the clusterwide file systems.
Therefore, we do not recommend placing the clusterwide root
file systems on a private bus.
Likewise, the quorum disk can be placed on the local bus of either of the member systems. If that member is not available, quorum can never be reached in a two-node cluster. We do not recommend placing the quorum disk on the local bus of a member system because it creates a single point of failure.
The individual member boot and swap partitions can also be placed on a local bus of either of the member systems. If the boot disk for member system 1 is on a SCSI bus internal to member 1, and the system is unavailable due to a boot disk problem, other systems in the cluster cannot access the disk for possible repair. If the member system boot disks are on a shared bus, they can be accessed by other systems on the shared bus for possible repair.
By placing the swap partition on a system's internal SCSI bus, you reduce total traffic on the shared bus by an amount equal to the system's swap volume.
TruCluster Server Version 5.1B configurations require one or more disks to hold the Tru64 UNIX operating system. The disks are either private disks on the system that will become the first cluster member, or disks on a shared bus that the system can access.
We recommend that you place the clusterwide root
file systems, member boot disks, and
quorum disk on a shared bus that is connected to all member
After installation, you have the option to reconfigure
swap and can place the swap disks on an internal SCSI bus to
manual for more information.
1.5.2 Two-Node Clusters Using UltraSCSI BA356 Storage Units with Increased Disk Configurations
The configuration shown in Figure 1-3 is a minimal configuration, with a lack of disk space for highly available applications. Starting with Tru64 UNIX Version 5.0, 16 devices are supported on a SCSI bus. Therefore, multiple BA356 storage units can be used on the same SCSI bus to allow more devices on the same bus.
shows the configuration in
with a second UltraSCSI
BA356 storage unit that provides an additional seven disks for highly
Figure 1-4: Two-Node Cluster with Two UltraSCSI DS-BA356 Storage Units
This configuration, while providing more storage, has
a single SCSI bus that presents a single point
Providing a second SCSI bus can allow
the use of the Logical Storage Manager (LSM) to mirror the
clusterwide root (
systems, and the data disks across SCSI buses, removing the single SCSI
bus as a single point of failure for these file systems.
1.5.3 Two-Node Configurations with UltraSCSI BA356 Storage Units and Dual SCSI Buses
By adding a second shared SCSI bus, you now have the capability to use
LSM to mirror data disks, and the
clusterwide root (
systems across SCSI buses.
You cannot use LSM to mirror the member system boot or quorum disks, but you can use hardware RAID.
shows a small cluster
configuration with dual SCSI buses using LSM to mirror the
clusterwide root (
and the data disks.
Figure 1-5: Two-Node Configurations with UltraSCSI BA356 Storage Units and Dual SCSI Buses
By using LSM to mirror the clusterwide root
file systems and the data disks, we
have achieved higher availability.
But, even if you have a
second cluster interconnect and redundant networks, because we
cannot use LSM to mirror the quorum or the member system boot
disks, we do not have a no-single-point-of-failure (NSPOF)
1.5.4 Using Hardware RAID to Mirror the Quorum and Member System Boot Disks
You can use hardware RAID with any of the supported RAID array
controllers to mirror the quorum and member system boot disks.
shows a cluster
configuration using an HSZ80 RAID array controller.
HSG60, HSG80, RAID array 3000 (with HSZ22 controller), or
Enterprise Virtual Array (with HSV110 controllers) can be used
instead of the HSZ80.
The array controllers can be configured as
a dual redundant pair.
If you want the capability to fail over
from one controller to another controller, you must install the
Also, you must set the failover mode.
Figure 1-6: Cluster Configuration with HSZ80 Controllers in Transparent Failover Mode
HSZ80, HSG60, or HSG80 has transparent failover mode enabled (
FAILOVER COPY = THIS_CONTROLLER).
In transparent failover
mode, both controllers are connected to the same shared bus and
Both controllers service the entire group of
storagesets, single-disk units, or other storage devices.
controller can continue to service all of the units if the other
The assignment of HSZ/HSG target IDs can be balanced between the controllers to provide better system performance. See the RAID array controller documentation for information on setting up storagesets.
In the configuration shown in
Figure 1-6, there is only one shared bus.
mirroring the clusterwide root and member boot disks, the single
shared bus is a single point of failure.
1.5.5 Creating an NSPOF Cluster
A no-single-point-of-failure (NSPOF) cluster can be achieved by:
Using two shared buses and hardware RAID to mirror the cluster file system
Using multiple shared buses with storage shelves and mirroring those file systems that can be mirrored with LSM, and by judicial placement of those file systems that cannot be mirrored with LSM.
To create an NSPOF cluster with hardware RAID or LSM and shared SCSI buses with storage shelves, you need to:
Install a second cluster interconnect for redundancy.
Install redundant power supplies.
Install redundant networks.
Connect the systems and storage to an uninterruptible power supply (UPS).
Additionally, if you are using hardware RAID, you need to:
Use hardware RAID to mirror the clusterwide root
file systems, the member boot disks, quorum disk (if
present), and data disks.
Use at least two shared buses to access dual-redundant RAID array controllers set up for multiple-bus failover mode (HSZ80, HSG60, HSG80, or Enterprise Virtual Array).
Only the HSZ80, HSG60, HSG80, and Enterprise Virtual Array are capable of supporting multiple-bus failover (
SET MULTIBUS_FAILOVER COPY = THIS_CONTROLLERfor the HSZ80, HSG60, and HSG80). The Enterprise Virtual Array supports only multiple-bus failover.
Partitioned storagesets and partitioned single-disk units cannot function in multiple-bus failover dual-redundant configurations with the HSZ80. You must delete any partitions before configuring the controllers for multiple-bus failover.
Partitioned storagesets and partitioned single-disk units are supported with the HSG60 and HSG80 with ACS V8.5 or later.
shows a cluster
configuration with dual-shared buses and a storage array with
If there is a failure in one SCSI bus, the
member systems can access the disks over the other SCSI bus.
Figure 1-7: NSPOF Cluster Using HSZ80s in Multiple-Bus Failover Mode
shows a cluster
configuration with dual-shared Fibre Channel buses and a storage
array with dual-redundant HSG80s configured for multiple-bus failover.
Figure 1-8: NSPOF Fibre Channel Cluster Using HSG80s in Multiple-Bus Failover Mode
If you are using LSM and multiple shared buses with storage shelves, you need to:
Mirror the clusterwide root (
systems across two shared buses.
Place the boot disk for each member system on a separate shared bus.
Provide another shared bus for the quorum disk.
shows a two-member cluster
configuration with three shared buses.
The clusterwide root
file systems are mirrored across the
first two shared buses.
The boot disk for member system one
is on the first shared bus.
The boot disk for member system
two is on the second shared bus.
The quorum disk is on the
third shared bus.
You can lose one system, or any one
shared bus, and still maintain a cluster.
Figure 1-9: NSPOF Cluster Using LSM and UltraSCSI BA356s
1.6 Eight-Member Clusters
TruCluster Server Version 5.1B supports eight-member cluster configurations as follows:
Fibre Channel: Eight-member systems may be connected to common storage over Fibre Channel in a fabric (switch) configuration.
Parallel SCSI: Only four of the member systems may be connected to any one SCSI bus, but you can have multiple SCSI buses connected to different sets of nodes, and the sets of nodes may overlap. We recommend you use a DS-DWZZH-05 UltraSCSI hub with fair arbitration enabled when connecting four-member systems to a common SCSI bus using RAID array controllers.
An eight-member cluster using Fibre Channel can be extrapolated easily from the discussions in Chapter 7; just connect the systems and storage to your fabric.
An eight-member cluster using shared SCSI storage is more complicated than Fibre Channel, and requires considerable care to configure. One way to configure an eight-member cluster using external termination is discussed in Chapter 12.
1.7 Overview of Setting Up the TruCluster Server Hardware Configuration
To set up a TruCluster Server hardware configuration, follow these steps:
Plan your hardware configuration. (See Chapter 3, Chapter 4, Chapter 7, Chapter 10, Chapter 11, and Chapter 12.)
Draw a diagram of your configuration.
Compare your diagram with the examples in Chapter 3, Chapter 7, Chapter 11, and Chapter 12.
Identify all devices, cables, SCSI adapters, and so forth. Use the diagram that you just constructed.
Prepare the shared storage by installing disks and configuring any RAID controller subsystems. (See Chapter 3, Chapter 7, and Chapter 11 and the documentation for the StorageWorks enclosure or RAID controller.)
Install signal converters in the StorageWorks enclosures, if applicable. (See Chapter 3 and Chapter 11.)
Connect storage to the shared buses. Terminate each bus. Use Y cables or trilink connectors where necessary. (See Chapter 3 and Chapter 11.)
For a Fibre Channel configuration, connect the HSG60, HSG80, or Enterprise Virtual Array controllers to the switches. You want the HSG60, HSG80, or Enterprise Virtual Array to recognize the connections to the systems when the systems are powered on.
Prepare the member systems by installing:
Additional Ethernet or Asynchronous Transfer Mode (ATM) network adapters for client networks.
The Fibre Channel adapter for Fibre Channel configurations.
Ensure that the Fibre Channel adapter is operating in the correct
Connect the Fibre Channel adapter to the switch or hub.
Connect the adapters you are using for the cluster interconnect to each other or to the Memory Channel or Ethernet hub or Ethernet switch as appropriate for your configuration. (See Chapter 5 or Chapter 6.)
Turn on the storage shelves, Memory Channel or Ethernet hubs or Ethernet switches, RAID array enclosures, and Fibre Channel switches, then turn on the member systems.
Install the firmware, set SCSI IDs, and enable fast bus speed as necessary. (See Chapter 4 and Chapter 10.)
Display configuration information for each member system, and ensure that all shared disks are seen at the same device number. (See Chapter 4, Chapter 7, or Chapter 10.)