HPE ProLiant DL325 Gen11 User Manual page 30

In the 4 SFF NVMe drive configuration:
Drives are assigned to box 1 and box 2.
SAS, SATA, or U.3 NVMe drives are supported.
When installing NVMe drives, install either all U.2 or all U.3 drives. Mixed NVMe drive type installation in the same box is not supported.
E3.S drive bay numbering E3.S drive bay numbering
20 E3.S 20 E3.S drive configuration drive configuration
The 20 E3.S 32G x4 NVMe UBM5 EC1 drive backplane option is supported in the E3.S drive configuration.
In the 20 E3.S drive configuration, all drives belong to the same box 1.
For more information on the drive backplane description, see Drive backplane naming.
8 8 E3.S E3.S drive configuration drive configuration
The 8 E3.S 32G x4 NVMe UBM5 EC1 drive backplane option is supported in the E3.S drive configuration.
In the 8 E3.S drive configuration, all drives belong to the same box 1.
For more information on the drive backplane description, see Drive backplane naming.
Drive backplane naming Drive backplane naming
This topic explains the features represented in the drive backplane naming. This naming convention was adopted starting in the HPE Gen11
server release. Your server might not support all the features listed in this topic. For server-specific support information, see the server
guides:
Drive backplane support, see Drive bay numbering.
HPE ProLiant DL325 Gen11 Server User Guide 30