PowerFlex 3.5: Failed Capacity With One SDS Flapping
Summary: Data failure with only one SDS decoupling.
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Symptoms
Networking issues cause MDM communication to arrive late, and SDS's don't know how to handle that.
Secondary comb holding SDS will reject a write from primary if combgen is not updated on the primary SDS.
One SDS decouples and data failure is printed in events.
SDS traces show:
26/10 17:10:47.495678 0x7fcbb28c2db0:raidComb_UpdateWriteError:00342: Write error comb 18a000328372, raid state 0x1, local rc SUCCESS, remote rc IO_FAULT_OLD_MIGRATE_GEN protType:SECONDARY, is trim ? No
26/10 17:10:47.495697 0x7fcbb28c2db0:raidComb_SetCombState:00129: Set comb raid state 18a000328372, raid state 0x1 => 0x10 (NORMAL => DEGRADED_REMOTE_ERROR) stateReason: SUCCESS
Impact
Data Unavailability (DU).
Cause
SDS's do not get combgen updates from MDM in any fashion that guarantees simultaneous receipt.
If the Primary SDS has an older combgen than the secondary (due to networking issues on primary SDS) the secondary will reject/refuse the write and the primary will ask to degrade the secondary's combs, and the MDM will agree.
Resolution
Workaround
None.
Impacted Versions
3.5
Fixed In Version
3.5.1.2
3.6
Article Properties
Article Number: 000195949
Article Type: Solution
Last Modified: 26 Nov 2025
Version: 6
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