Write-Cache Policy For Cisco 12G Sas Modular Raid Controllers; Mixing Drive Types In Raid Groups; Drive Type Mixing Best Practices - Cisco UCS C240 M5 Installation And Service Manual

Write-Cache Policy for Cisco 12G SAS Modular RAID Controllers

Write-Cache Policy for Cisco 12G SAS Modular RAID Controllers
For this server and other Cisco Generation M5 servers, the default write-cache policy for the Cisco Modular
RAID controllers is Write Through (irrespective of the presence of a charged supercap or "good BBU"). This
utilizes the optimal performance characteristics of the controller.
The write policy can be set to Write Back, if preferred. You can set the write policy using the following
methods:
• For standalone servers, use the Cisco IMC interface to set Virtual Drive Properties > Write Policy. See
• For Cisco UCS-integrated servers, use the Cisco UCS Manager interface to set the write-cache policy
• Use the LSI Option ROM Configuration Utility.

Mixing Drive Types in RAID Groups

The following table 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.
Table 17: Mixing Drive Types
Mix of Drive Types in RAID Group
SAS HDD + SATA HDD
SAS SSD + SATA SSD
HDD + SSD

Drive Type Mixing Best Practices

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.
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the "Managing Storage Adapters" section in your Cisco IMC Configuration Guide.
Cisco IMC GUI and CLI Configuration Guides
as part of virtual drive configuration in your storage profile.
Cisco UCS Manager Configuration Guides
Storage Controller Considerations
Allowed?
Yes
Yes
No