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Cisco Bug: CSCul59456 - Major alarm "Drive state: cache degraded" on rack servers

Last Modified

Sep 05, 2019

Products (1)

  • Cisco Unified Computing System

Known Affected Releases

2.2(0.370)A 2.2(0.370)C

Description (partial)

A fault is raised with the text "Drive state: cache degraded".

This fault is raised on systems with a storage controller that is
capable of having a BBU but either doesn't have one present or
has one but it is in a bad state.

When UCSM creates a virtual drive, it uses the default settings
from LSI. For controllers that support a BBU, the default setting
for write cache policy is "Write Back Good BBU". (LSI's term is "Write Back").

If there is no BBU present, then the actual write cache policy becomes
"Write Through". This means that the system is operating at
a degraded performance level because data must be physically
written to the drive before the host is informed that the
write succeeded.
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