Capacity design when adding drives (for Mirroring)

Virtual Storage Platform One SDS Block Storage Administrator Guide
Version
1.17.x
Audience
anonymous
Part Number
MK-24VSP1SDS002-04

Describe about capacity design when adding drives for Mirroring.

The following is assumed:

  • The effective physical capacity of the added drives is uniform and is added to all storage nodes.

  • The cluster does not have faulty storage nodes or faulty drives.

  • The configuration, the capacity of each storage node, and the number of drives meet the system requirements.

    For details about storage node requirements, see Storage node requirements in the VSP One SDS Block Setup and Configuration Guide for the model that you are using.

  1. Calculate the valid physical capacity of the added drive by using the method described in Capacity design principles (1) : Physical capacity (for Mirroring).
  2. The increased logical capacity of the added drive can be calculated by: 
    Total logical capacity after adding drives[MiB] 
    = C + RoundDown((R + A -198576 - CrawDevice × Nrebuild) / 198576) × N × 99288
    C: Total logical capacity before adding drives
    RoundDown(numerical value)
        : A numerical value is rounded down to an integer.
    R: Reserved physical capacity of each storage node before adding 
        drives
    A: Valid physical capacity of each storage nodes before adding 
        drives
    N: Number of storage nodes
　　CrawDevice: Valid physical capacity [MiB/device]
　　Nrebuild: Tolerable number of drive failures set for the storage pool (0 if the rebuild capacity policy is set to "Variable")

    Note that the capacity that a storage controller can manage has an upper limit. The capacity exceeding the following values cannot be used as logical capacity.

    1001567424 × the number of storage nodes [MiB]