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C-5
Cisco UCS C220 Server Installation and Service Guide
OL-25760-01
Appendix C RAID Controller Considerations
Mixing Drive Types in RAID Groups
Mixing Drive Types in RAID Groups
Following are the rules for mixing hard disk drive (HDD) and solid state drive (SSD) types in a RAID
group.
RAID Backup Units
This server supports installation of one RAID battery backup unit (BBU) or one SuperCap Power
Module (SCPM). The unit mounts to a holder on the left-side air baffle (see
Figure 3-24).
• The optional LSI BBU is available only when using the LSI MegaRAID controller cards. This BBU
provides approximately 72 hours of battery backup for the disk write-back cache DRAM in the case
of sudden power loss.
• The optional SCPM is available only when using the LSI MegaRAID-CV controller cards. This
supercap module provides approximately 3 years of backup for the disk write-back cache DRAM in
the case of sudden power loss by offloading the cache to the NAND flash.
Ta b l e C-5 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