Cisco UCS C220 M4

C-6
Cisco UCS C220 M4 Server Installation and Service Guide
OL-32473-01
Appendix C RAID Controller Considerations
Mixing Drive Types in RAID Groups
Mixing Drive Types in RAID Groups
Table C-2 lists the technical capabilities for mixing hard disk drive (HDD) and solid state drive (SSD)
types in a RAID group. However, see the recommendations that follow for the best performance.
Mixing Drive Types in RAID Groups
For the best performance, follow these guidelines:
• Use either all SAS or all SATA drives in a RAID group.
• Use the same capacity for each drive in the RAID group.
• Never mix HDDs and SSDs in the same RAID group.
RAID Backup Units
This server supports installation of one supercap Power Module (SCPM). The unit mounts to a bracket
in-line with the fan modules (see Figure 3-20).
The optional SCPM provides approximately three years of backup for the disk write-back cache DRAM
in the case of a sudden power loss by offloading the cache to the NAND flash.
For SCPM replacement instructions, see Replacing the Supercap Power Module (RAID Backup),
page 3-33.
Table C-2 Drive Type Mixing in RAID Groups
Mix of Drive Types
in RAID Group Allowed?
SAS HDD + SATA HDD Yes
SAS SSD + SATA SSD Yes
HDD + SSD No