Dell EMC PowerEdge C6520 Installation And Service Manual page 14

Figure 16. 2.5-inch NVMe backplane chassis with one C6520 sled with up to 2 NVMe drives
C6400 chassis - No backplane
The C6400 chassis with No-backplane configuration is optimized for use cases that require little to no local storage and primarily
use external storage. Each C6520 sled in this chassis can still be optionally configured with a local M.2 boot drive. This chassis
does not come with a drive backplane and no front drives are supported for any C6520 sled. Not having a drive backplane
maximizes air flow to the C6520 sleds, hence this configuration is the most thermally flexible among all chassis options.
The C6400 chassis with No-backplane a good fit for use cases such as HPC, High Frequency Trading, SaaS/IaaS with external
storage, Hadoop data node with external HDFS storage (such as Isilon).
Figure 17. C6400 chassis - No backplane
C6400 chassis - 12 x 3.5-inch Direct Backplane drive configuration
The C6400 chassis with 12 x 3.5-inch direct backplane enables a total of 12 drives and up to 3 drives per C6520 sled.
NOTE:
● The chassis is optimized for high performance compute and cost effective large capacity storage.
● Using an M.2 boot drive in each C6520 sled enables use of front 3.5-inch drives entirely for application data.
● an NVMe PCI card can be used in the LP slot in each C6520 to provide high performance storage for say writes/cache.
This makes the C6400 chassis with a 3.5-inch backplane a good fit for use cases such as Software Defined Storage,
Hyper Converged Infrastructure, High Performance Computing nodes that need large storage.
Figure 18. C6400 chassis - 12 x 3.5-inch Direct backplane
C6400 chassis - 3.5-inch Direct backplane chassis - Drive enumeration
14 Dell EMC PowerEdge C6520 system overview