Resolve “Read and Write Cache Are Currently Down” on Dell SCv2020 Storage

What This Guide Covers

This article provides a clear, structured walkthrough for diagnosing and resolving situations where read and/or write cache becomes unavailable on Dell SCv2020 storage systems. The information is based on documented behaviors and verified solutions discussed in Dell Community forums and Dell technical resources.

Quick Fix Summary

• Verify controller cache battery health and replace if depleted.
• Update SCOS firmware to the latest supported version for your system.
• If cache remains down, run cache‑related commands or engage Dell Support for log analysis.

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Overview

The SCv2020 uses mirrored cache modules supported by battery backup to ensure data integrity. If a controller detects a hardware, battery, or software condition that may limit cache protection, the system may temporarily disable read and/or write cache as a safety measure. This behavior is intentional and designed to protect data during abnormal events (for example, power irregularities, firmware inconsistencies, or recovery states).

Error Indicators

Common warning messages include:

• “Read and Write Cache are currently down on this Storage Center.”
• “Write cache is currently down on the Storage Center.”
• “An unrecoverable problem was found with caching hardware on controller … during system startup.” 

Additional symptoms:

• Slower than normal write performance.
• System shows cache status as Down when running diagnostic commands like cache status. 

Possible Causes

• Controller cache battery not charged, depleted, or previously failed
  Cache may remain disabled until batteries are healthy.
• Software or firmware requiring update
  Certain cache states may be resolved via SCOS firmware updates.
• UPS or power‑event conditions
  If a UPS enters battery mode, write cache may be disabled until the system confirms stable power.
• Internal controller cache state mismatch
  May require internal cache reset or command‑line intervention.
• Hardware abnormalities detected on cache modules
  Controller startup diagnostics may suppress cache activation.

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Troubleshooting Steps

1. Confirm Cache Battery Health (Most Common Fix)

1. Log into Storage Manager.
2. Inspect both controllers’ battery modules.
3. Replace any battery that shows failure or low health.
   • Cache will not enable unless batteries are operational.
4. After replacement, allow batteries to fully charge and reboot controllers if needed.

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2. Update Firmware / SCOS Version

1. Check current SCOS version.
2. Apply the latest SCOS firmware supported for your SCv2020.
   • Firmware updates address known cache‑state issues.
3. Reboot storage controllers following update completion.

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3. Run Cache Internal State Reset (Advanced)

If batteries and firmware are healthy and cache remains down:

1. Connect to the controller console.
2. Run: cache resetinternalstate 1
   • This command has been used to restore cache operation in some cases. 
3. Re-check status using: cache status

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4. Review Power Infrastructure / UPS Alerts

1. Inspect UPS logs for recent “on battery” events.
2. Ensure normal power operation has been restored.
3. If the Storage Center detected a UPS battery event, cache may remain disabled until the system verifies stable power.

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5. Engage Dell Support (When Applicable)

If under support:

• Provide controller serial numbers and phone‑home logs for analysis.
• Cache‑related issues may require deeper diagnostics.

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Additional Notes

• Even end‑of‑life (EOL) systems may require specialized command execution that only support personnel traditionally perform.
• Cache disablement is a protective behavior, not a failure indicator.
• Always maintain proper controller battery replacements with Dell‑supported parts.

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References

• SCv2020 – Read and Write Cache Down
• Related  SCv2020 Cannot Enable Cache