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Enabling the SPDK feature in Longhorn requires additional CPU and memory resources, making it unsuitable for all environments. To address this, Longhorn provides a global setting that enables or disables the SPDK feature, which is disabled by default.

When the feature is enabled, Longhorn attempts to prevent updates to this setting while there are volumes attached. When the setting is applied, Longhorn restarts all instance-manager pods to ensure that the SPDK feature is properly enabled or disabled.

• Add a global setting spdk for enabling/disabling SPDK feature
• Add a global setting spdk-hugepage-limit for configuring hugepage size used by SPDK
• Validate node conditions such as hugepage and kernel driver before creating the instance-manager supporting spdk

cc @shuo-wu @innobead

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