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 VSP One Capacity question

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Javier Camargo Soto's profile image
Javier Camargo Soto posted 01-08-2026 18:27

Good afternoon,

 I need your help calculating the usable capacity of a VSP B28 with the following configuration:

I intend to purchase storage with 49 60TB disks and need to calculate the usable capacity it will give me after creating the pool.

I understand that I need to create two DDP groups, one with 32 disks and another with 17. Can these be in the same pool, or will each DDP have its own pool?

I'll be waiting, thank you very much.

Best regards.

Antonius Schwefer's profile image
Antonius Schwefer posted 01-09-2026 15:26  Best Answer

Good evening,

a pool can contain up to 4 DDP groups.

The usable capacity can be calculated like this (RAID 6 6D+2P):

(Number of drives - 1) driveCapacity  * 0,75 

It makes sense to create two DDPs with similiar capacity (24 and 25 drives for example).

This is possible by RAIDCOM only, because VSP One Block Administrator would create one DDP with 32 and another with 17 drives.

The usable capacity for a DDP with 24 60TB drives with 6D+2P will be roughly:

23*60TB*0,75 = 1035TB 

Best regards from snowy Germany

Toni

Mark Perino's profile image
Mark Perino posted 01-16-2026 11:45

Some clarification here. 
On the latest microcode, you do not NEED to perform this task using the command line or via REST API.  You can create a DDP Pool in the GUI.
On B28 up to 2 DDP in the same Pool are supported. In RAID-6 Each DDP may contain up to 32 drives (which creates a max of 64 drives in a pool).

The limitations of creating DDP pools on B28 are documented in the Virtual Storage Platform One Block Administrator User Guide:
https://docs.hitachivantara.com/r/en-us/virtual-storage-platform-one-block/a3-04-0x/mk-23vsp1b001/configuring-storage-resources/creating-a-pool 

In your case using the GUI and selecting 49 HDD, will create 2x DDP in the same pool.  Each DDP will loose 2 disks of capacity for RAID-6 Parity, and 1 of disk of capcity each for Spare.  So the Usable Capacity before enabling ADR will be around 60*[49 - 2x(2+1)] or approx: 43x60.
Keep in mind that you will also lose capacity within the pool for the Fingerprint Volumes (4x), and Data Store Devices(4x) needed for ADR:

"When Deduplication is enabled, duplicated data among virtual volumes associated with a pool is deleted (deduped). When a pool with virtual volumes Deduplication enabled is created, deduplication system data volumes (Fingerprint) and deduplication system data volumes (Data Store) are automatically created. The deduplication
system data volume (Fingerprint) stores a table to search for duplicated data among data stored in the pool. Four deduplication system data volumes (fingerprint) are created per pool. The deduplication system data volume (data store) stores the original data of any duplicated data. Four deduplication system data volume (data
store) are created per pool. "

You can create 2 x DDPs manually in the CLI if you like, to balance out the number of disks in each DDP.  However it is not a requirement.