The base extension is part of the default installation option as it controls the various program products and serves as control area. So the short answer is no, there is no supported configuration without the base extension. Let me explain briefly why that is.
Shared memory houses metadata and system tables for Dynamic Provisioning and Dynamic Tiering, deduplication and parity just to name a few. It also controls mirroring for write data (I/O cache as you referenced) and inter-controller communication. This is also the area where advanced feature sets such as dedupe and compression, Thin Image snapshots and GAD are handled.
Lastly, you cannot deselect the base extension as it is greyed out under the SM installation screen via the GUI for the above stated reasons. For B24, Extension 1 is not available. Extension 1 is available in B26 and Extension 2 for B28 models due to the larger configurable cache options and physical storage expansion.
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David Jontow
Hitachi Vantara
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Original Message:
Sent: 07-17-2026 05:05
From: Sarath Palleeluveedu
Subject: Shared memory allocation on VSP One Block 24Q
Thank you David, Is allocation of the Shared Memory Base function mandatory on the VSP One B24Q, or is there a supported configuration that allows operation without it?
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Sarath
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Original Message:
Sent: 07-16-2026 12:59
From: David Jontow
Subject: Shared memory allocation on VSP One Block 24Q
Hi Sarath,
You are partially correct. The base allocation is 174GB and also uses an additional ~24GB for cache DIR size. This leaves approximately 57.5GB data(I/O) cache. Other system functions are handled within the base extension allocation.
I hope this helps.
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David Jontow
Hitachi Vantara
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