Storage configuration planning

Complete all storage configuration planning tasks before you configure your system environment.

Planning the systems

Determine:
  • The number of systems and the number of node pairs (I/O groups). Each pair of nodes is the container for one or more volumes.
  • The number of hosts to use.
  • The number of I/Os per second between the hosts and nodes.

Planning the hosts

Host mapping provides a way for hosts to access specific logical units (LUs) within the storage systems. Determine:
  • For hosts that use a Small Computer System Interface (SCSI) over Fibre Channel connection, the worldwide port names (WWPNs) of the Fibre Channel (HBA) ports are on the hosts.
  • For hosts that use an Internet Small Computer System Interface (iSCSI) over Ethernet connection, the iSCSI qualified name (IQN) of the host and the authentication credentials.
  • The names to assign to the hosts.
  • The volumes to assign to the hosts.
  • For hosts that use a SCSI over Fibre Channel over Ethernet (FCoE) connection, the WWPNs of the Converged Network Adapter (CNA) ports are on the hosts.

Planning the MDisks

To plan the managed disks (MDisks), determine:
  • The logical or physical disks (logical units) in the storage systems
  • The logical units structure
  • Technology type
  • Whether the drives are flash drive.
  • Whether the internal MDisks must not lose redundancy to maintain performance

Planning the storage pools

Necessary activities:
  • Determine the types of storage systems to use.
  • To create volumes with the sequential policy: plan to create a separate storage pool for these volumes, or ensure that you create these volumes before you create volumes with the striped policy.
  • Plan to create storage pools for the storage systems that provide the same level of performance, reliability, or both performance and reliability. For example, group all of the managed disks that are RAID 10 in one storage pool and all of the MDisks that are RAID 5 in another storage pool.
  • Plan whether to create storage pools that have multiple tiers of storage. Multiple tiers of storage include both flash drive based volumes and normal hard disk drive (HDD) volumes that are managed by Easy Tier®. In multiple-tiered storage pools, plan to create the same level of performance, reliability, or both performance and reliability within each tier.
  • Plan the extent size of the storage pool. For example, a larger extent size increases the total amount of storage that the system can manage. A smaller extent size provides more fine-grained control of storage allocation. Extent size does not affect performance.
  • If you are attaching more than 4 PB of storage to a system, you are not able to use all this capacity with the default extent size of 1 GB. Run the following CLI command one time to enable support for larger extent sizes in the GUI. 
    chsystem -guiadvancedpool yes

Planning the volumes

An individual volume is a member of one storage pool and one I/O group. The storage pool defines which MDisks provide the back-end storage that makes up the volume. The I/O group defines which nodes provide I/O access to the volume.

Consider the effect that FlashCopy®, Global Mirror, Metro Mirror, and thin-provisioned volumes have on performance. The effect depends on the type of I/O, and is calculated by using a weighting factor.

Compressed volumes are a special type of volume where data is compressed as it is written to the volume, saving extra space. To use the compression function, you must obtain the IBM® Real-time Compression license.

Before you purchase a compression license, you can use the analyzevdiskbysystem command to determine potential compression savings for your current environment. Single volumes can also be analyzed for compression savings by using the analyzevdisk command. Both of these commands are available and do not require a compression license.