- Atomic Write Unit Normal (AWUN) 描述了 atomic write 的最大单位 小于 AWUN 的 write 操作都是 atomic 的
- Atomic Write Unit Power Fail (AWUPF) 描述了 powerfail 情况下的 atomic write 的最大单位
Atomic Write Unit Normal (AWUN): This field indicates the size of the write operation guaranteed to be written atomically to the NVM across all namespaces with any supported namespace format during normal operation. This field is specified in logical blocks and is a 0’s based value.
If a specific namespace guarantees a larger size than is reported in this field, then this namespace specific size is reported in the NAWUN field in the Identify Namespace data structure.
If a write command is submitted with size less than or equal to the AWUN value, the host is guaranteed that the write command is atomic to the NVM with respect to other read or write commands. If a write command is submitted with size greater than the AWUN value, then there is no guarantee of command atomicity.
Atomic Write Unit Power Fail (AWUPF): This field indicates the size of the write operation guaranteed to be written atomically to the NVM across all namespaces with any supported namespace format during a power fail or error condition.
If a specific namespace guarantees a larger size than is reported in this field, then this namespace specific size is reported in the NAWUPF field in the Identify Namespace data structure.
This field is specified in logical blocks and is a 0’s based value. The AWUPF value shall be less than or equal to the AWUN value.
If a write command is submitted with size less than or equal to the AWUPF value, the host is guaranteed that the write is atomic to the NVM with respect to other read or write commands. If a write command is submitted that is greater than this size, there is no guarantee of command atomicity. If the write size is less than or equal to the AWUPF value and the write command fails, then subsequent read commands for the associated logical blocks shall return data from the previous successful write command. If a write command is submitted with size greater than the AWUPF value, then there is no guarantee of data returned on subsequent reads of the associated logical blocks.
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