6.1.2 Points to consider when setting up an LVM

This subsection explains the points to consider when setting up an LVM. For details about how to set up an LVM, see the documentation for the operating system you are using.

• Assign access privileges to the HADB administrator you set up in the OS in 8.2.1 Tasks that must be performed before installation so the HADB administrator can access the logical volume (LV).

  If the logical volume was created by the LVM, its access privilege information might be initialized each time the OS is restarted. Therefore, after restarting the OS, make sure that the access privilege has not been reinitialized.

• To improve the processing performance, use as many disks as possible for striping. Increasing the number of disks distributes the disk storage locations more widely, and therefore reduces the number of I/O operations on each disk, which in turn improves the processing performance.

• When a single DB area is configured across multiple logical volumes (DB area files), accesses to the logical volumes are distributed, resulting in improved processing performance. A guideline for determining the number of logical volumes to configure for a single DB area is 20 to 40 percent of the number of CPU cores in the machine in which the HADB server is installed. For example, if the number of CPU cores in the machine is 40, use 8 to 16 logical volumes to configure a single DB area.

• We recommend that you specify 4,096 kilobytes for the stripe size for LVMs. If you specify a different value, specify one that is at least the DB area page size, does not exceed 16,384 kilobytes, and is an integer multiple of the DB area page size.

• If the data storage locations are sufficiently distributed by storage functions, there is no need to use the LVM to implement a striping configuration just to distribute I/O operations.

  If a striping configuration that stores data across multiple RAID groups cannot be implemented by storage functions, use LVMs to implement striping. For example, if there are 60 disks and the maximum number of disks that can make up one RAID group is 15, create four RAID groups and configure striping for each RAID group.

• To prevent degradation of processing performance due to access contention, we recommend that the size of one logical volume (DB area file) does not exceed 16 terabytes.

• When using the multi-node function or a cold standby configuration, if you are using SCSI reservation for shared disk, specify SCSI reservation at the storage disk (RAID group) level. Areas subject to SCSI reservation must be on a separate disk from other areas. For details about areas subject to SCSI reservation, see the following topics:

  • When using the multi-node function: 16.2.4 Storage configuration

  • When using a cold standby configuration: 17.2.4 Storage configuration

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