ExpressCluster X 3.1 for Linux Getting Started Guide - Nec

Designing a system configurationHardware requirements for mirror disksDisks to be used as a mirror disk resource do not support a Linux md stripe set, volume set,mirroring, and stripe set with parity.Mirror disk resource cannot be made as a target of a Linux md stripe set, volume set,mirroring, and stripe set with parity.Mirror partitions (data partition and cluster partition) to use a mirror disk resource.There are two ways to allocate mirror partitions:• Allocate a mirror partition (data partition and cluster partition) on the disk where theoperating system (such as root partition and swap partition) resides.• Reserve (or add) a disk (or LUN) not used by the operating system and allocate a mirrorpartition on the disk.Consider the following when allocating mirror partitions:• When maintainability and performance are important:- It is recommended to have a mirror disk that is not used by the OS.• When LUN cannot be added due to hardware RAID specification or when changingLUN configuration is difficult in hardware RAID pre-install model:- Allocate a mirror partition on the same disk where the operating system resides.When multiple mirror disk resources are used, it is recommended to prepare (adding) a diskper mirror disk resource. Allocating multiple mirror disk resources on the same disk mayresult in degraded performance and it may take a while to complete mirror recovery due todisk access performance on Linux operating system.Disks used for mirroring must be the same in all servers.• Disk typeMirror disks on both servers and disks where mirror partition is allocated should be ofthe same disk typeFor supported disk types, see “Supported disk interfaces” on page 52.ExampleCombination server1 server2OK SCSI SCSIOK IDE IDENG IDE SCSINotes when the geometries of the disks used as mirror disks differ between the servers.The partition size allocated by the fdisk command is aligned by the number of blocks(units) per cylinder. Allocate a data partition considering the relationship between datapartition size and direction for initial mirror configuration to be as indicated below:Source server ≤ Destination server“Source server” refers to the server where the failover group that a mirror disk resourcebelongs has a higher priority in failover policy. “Destination server” refers to the serverwhere the failover group that a mirror disk resource belongs has a lower priority infailover policy.Section II Installing ExpressCluster109