IBM Cloud block storage overview

IBM Cloud® block storage provides iSCSI block storage LUNs that range in size from 20 GB through 12 TB and in levels of input/output operations per second (IOPS).

Block Storage IOPS Options

Block storage IOPS can be provisioned in either “Endurance” IOPS tiers or as “Performance” custom allocated IOPS.

When you choose Endurance, volumes are provisioned in one of four storage tiers that are defined by their I/O density: 0.25, 2.0, 4.0 and 10.0 IOPS per GB, with the first tier provisioned on spinning disk and the remaining tiers on flash storage.

When you choose Performance, you can select the storage volume size and separately specify the total number of IOPS entitled on the volume. IOPS are provisioned in increments of 100 and can range from as low as 100 to as high as 48,000 per single volume. However, the complete range of IOPS values is not available for all volume sizes.

A range of available IOPS exists for each defined LUN volume size. Smaller volumes have a lower maximum IOPS. Conversely, larger volumes have higher minimum IOPS. For more information about the available IOPS to capacity ranges, see the IBM Cloud block storage documentation at Getting started with Block Storage.

Develop a target capacity and I/O storage density goal

While you plan your IBM Spectrum Virtualize for Public Cloud deployment, research the intended use of the storage you are provisioning to determine a target capacity and anticipated IO storage density from the requirements. In a typical customer environment, the data center has multiple tiers of storage and a usage profile that defines the percentage of total capacity in each tier.

When you plan implementation of an IBM Spectrum Virtualize for Public Cloud infrastructure, you can provision multiple storage volumes with a combined capacity that provides the capacity and IOPS goals that are required. IBM Spectrum Virtualize for Public Cloud distributes the I/O workload over multiple volumes that are allocated in a disk group, with a preference for multiples of four. For example, four 500 GB LUNs might be provisioned, with each LUN delivering 4000 IOPS and the disk group providing 2 TBs and 16,000 IOPS. That provision is 8 IOPS per GB storage density, which might be the requirement you were targeting for a tiered class of service.

Alternatively, 8 x 250 GB volumes where each LUN delivers 2000 IOPS would also meet the same IOPS per GB requirement. When exact multiples of four disks do not meet your requirements, you can also use multiples of two disks. Disk groups should not be provisioned with odd numbers of disks in the group.

Before you provision the storage for your implementation, you can determine appropriate number, size, and IOPS that you require for the volumes in your disk groups. Performance storage provides much greater flexibility for selecting both a capacity and IOPS per LUN. However, if you require storage at a specific storage tier, Endurance storage might provide a simpler solution. IBM Spectrum Virtualize for Public Cloud can use both offerings interchangeably, as it aggregates both the capacity and the IOPS of the LUNs that are configured in a disk group.