Dell EMC Unity: How to customize the Hot Spare policy (User Correctble)
Summary: Unity leverages global sparing, where any unbound drive is eligible to be used as a hot spare. It is important to consider the requirements for hot spares when designing storage pool layouts. The hot spare policy applies to each drive type, size, and speed and cannot be changed. ...
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Instructions
Unity enforces a hot spare policy of one out of every thirty drives of a given type.
Initial Release - This means if there are thirty drives available, twenty-nine can be used for a pool since the last one must be left unbound as a hot spare. If thirty-one drives are available, two must be left unbound as hot spares. In order to create a thirty-drive pool, thirty-two drives are required, as two hot spares are needed.
Unity OE 4.0.1.8194551 or later, the hot spare policy reserves one out of every thirty-one drives. This means
if there are thirty-one drives available, only one is must be left unbound for the hot spare and the remaining 30 can be used in a pool.
Initial Release - This means if there are thirty drives available, twenty-nine can be used for a pool since the last one must be left unbound as a hot spare. If thirty-one drives are available, two must be left unbound as hot spares. In order to create a thirty-drive pool, thirty-two drives are required, as two hot spares are needed.
Unity OE 4.0.1.8194551 or later, the hot spare policy reserves one out of every thirty-one drives. This means
if there are thirty-one drives available, only one is must be left unbound for the hot spare and the remaining 30 can be used in a pool.
Additional Information
see the Unity High Availability paper in the Hot Spares section on Page 12:
https://support.emc.com/docu71319_Unity:-High-Availability---A-Detailed-Review.pdf?language=en_US
Affected Products
Dell EMC Unity FamilyProducts
Dell EMC Unity FamilyArticle Properties
Article Number: 000022659
Article Type: How To
Last Modified: 16 Oct 2025
Version: 3
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