Storage Capacity Virtualization

Thin Provisioning improves the usability of the drives by managing the physical drives in a pool, and sharing the unused capacity among the virtual volumes in the pool. The volume capacity that is seen from the server is virtualized to allow the server to recognize a larger capacity than the physical volume capacity. Because a large capacity virtual volume can be defined, the drives can be used in a more efficient and flexible manner.

Initial cost can be reduced because less drive capacity is required even if the capacity requirements cannot be estimated. The power consumption requirements can also be reduced because a fewer number of drives are installed.

Figure: Storage Capacity Virtualization

In the Thin Provisioning function, the RAID group, which is configured with multiple drives, is managed as a Thin Provisioning Pool (TPP). When a write request is issued from the host, a physical area is allocated to the virtual volume. The free space in the TPP is shared among the virtual volumes which belong to the TPP, and a virtual volume, which is larger than the drive capacity in the ETERNUS DX, can be created. A virtual volume to be created in a TPP is referred to as a Thin Provisioning Volume (TPV).

• Thin Provisioning Pool (TPP)

  A TPP is a physical drive pool which is configured with one or more RAID groups. TPP capacity can be expanded in the units of RAID groups. Add RAID groups with the same specifications (RAID level, drive type, and number of member drives) as those of the existing RAID groups.

  The following table shows the maximum number and the maximum capacity of TPPs that can be registered in the ETERNUS DX.

  Table: TPP Maximum Number and Capacity

  Item	ETERNUS DX600 S6	ETERNUS DX900 S6 ETERNUS DX8900 S6
  Maximum number of pools (*1)	256	256
  Maximum pool capacity (*2)	98,304TB (96PB)	524,288TB (512PB)

  *1	:	The maximum total number of Thin Provisioning Pools and FTSPs.
  *2	:	The maximum pool capacity is the capacity that combines the FTSP capacity and the Thin Provisioning Pool capacity in the ETERNUS DX.

  The following table shows the TPP chunk size that is applied when TPPs are created.

  Table: Chunk Size According to the Configured TPP Capacity

  Setting value of the maximum pool capacity		Chunk size (*1)
  ETERNUS DX600 S6	ETERNUS DX900 S6 ETERNUS DX8900 S6
  Up to 1,536TB	Up to 8,192TB	21MB
  98,304TB (96PB) (*2)	524,288TB (512PB) (*2)	1,344MB (the default value is 21MB when the Deduplication function or the Compression function is enabled)

  *1	:	Chunk size is for delimiting data. The chunk size is automatically set according to the maximum pool capacity.
  *2	:	If the maximum pool capacity is set to 512PB (or 96PB for the ETERNUS DX600 S6), the chunk size can be manually set when pools are created. The available chunk size values and the TPP capacity that can be created are shown below. Chunk size TPP capacity that can be created ETERNUS DX600 S6 ETERNUS DX900 S6 ETERNUS DX8900 S6 21MB 1.5PB 8PB 42MB 3PB 16PB 84MB 6PB 32PB 168MB 12PB 64PB 336MB 24PB 128PB 672MB 48PB 256PB 1,344MB 96PB 512PB

  To perform encryption, specify encryption by firmware when creating a TPP, or select the Self Encrypting Drive (SED) for configuration when creating a TPP.

  The following table shows the RAID configurations that can be registered in a TPP.

  Table: Levels and Configurations for a RAID Group That Can Be Registered in a TPP

  RAID level	Number of configurable drives	Recommended configurations
  RAID0	4 (4D)	—
  RAID1	2 (1D+1M)	2 (1D+1M)
  RAID1+0	4 (2D+2M), 8 (4D+4M), 16 (8D+8M), 24 (12D+12M)	8 (4D+4M)
  RAID5	4 (3D+1P), 5 (4D+1P), 7 (6D+1P), 8 (7D+1P), 9 (8D+1P), 13 (12D+1P)	4 (3D+1P), 8 (7D+1P)
  RAID6	6 (4D+2P), 8 (6D+2P), 9 (7D+2P), 10 (8D+2P)	8 (6D+2P)
  RAID6-FR	13 ((4D+2P) × 2 + 1HS), 17 ((6D+2P) × 2 + 1HS) 31 ((8D+2P) × 3 + 1HS), 31 ((4D+2P) × 5 + 1HS)	17 ((6D+2P) × 2 + 1HS)

• Thin Provisioning Volume (TPV)

  The maximum capacity of a TPV is 128TB. Note that the total TPV capacity must be smaller than the maximum capacity of the TPP.

  When creating a TPV, the Allocation method can be selected.

  • Thin

    When data is written from the host to a TPV, a physical area is allocated to the created virtual volume. The allocated capacity size (chunk size) is the same as the chunk size of the TPP specified when a TPV is created. The physical storage capacity can be reduced by allocating a virtualized storage capacity.

  • Thick

    When creating a volume, the physical area is allocated to the entire volume area. This can be used for volumes in the system area to prevent a system stoppage due to a pool capacity shortage during operations.

  In general, selecting "Thin" is recommended. The Allocation method can be changed after a TPV is created.

  Perform a TPV/FTV capacity optimization if "Thick" has changed to "Thin". By optimizing the capacity, the area that was allocated to a TPV is released and the TPV becomes usable. If a TPV/FTV capacity optimization is not performed, the usage of the TPV does not change even after the Allocation method is changed.

  The capacity of a TPV can be expanded after it is created.

  For details on the number of TPVs that can be created, refer to Volume.