Hi,
This is referring to the write-cache on the disk controller.If you have a dead battery you will have write-cache disabled and it will affect performance.
Its a hardware replacement at the end of the day.
See below
Write-Cache
A disabled write-cache on the server also causes the upgrade process to run more slowly. Multiple factors, including dead batteries on older servers, can cause the write-cache to get disabled.
Before starting an upgrade, verify the status of the write-cache on the MCS-7828-H4 and MCS-7835/45 disk controllers. You do not need to verify the write-cache status on the MCS-7816, MCS-7825, or other MCS-7828 servers. To verify write-cache status, access the Cisco Unified Operating System Administration, and choose Show > Hardware.
If you determine that your write-cache is disabled because of a dead battery, you need to replace the hard disk controller cache battery. Follow your local support procedures to get this battery replaced.
See the following examples of output from the Show > Hardware menu for details on determining the battery and write-back cache status.
The following example shows write-cache enabled. The example indicates that 50 percent of the cache is reserved for write and 50 percent of the cache is reserved for read. If the write-cache was disabled, 100 percent of the cache would be reserved for read or the Cache Status would not equal "OK". Also, the battery count equals "1". If the controller battery was dead or missing, it would indicate "0".
cheers
Mark
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