DELL Unity: New Data Is Missing in the Source LUN and Snapshots

Summary: Customer found that data in source LUN was out-of-date, while checking all its snapshots, the data was as old as the source LUN.

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Symptoms

  1. While mounting every snapshot into the host to check data, all snapshots showed the same old data  as the source LUNs.
  2. By checking source LUN  and snapshots space usage, only snapshot space usage  increased.
 - 2020.11.16
PrimaryDataConsumptionInBlocks  (Sectors)  : 6699264416   <<< Source LUN size
SecondaryDataConsumption (Sectors)         :    1000598176   <<< snapshot  size

- 2021.04.02
PrimaryDataConsumptionInBlocks  (Sectors)  : 6699264416  <<< Source LUN size
SecondaryDataConsumption (Sectors)         :     3483567376 <<< snapshot  size

Cause

  1. Five months ago,  Data was restored from a snapshot by attaching that  snapshot to the same host with read/write mode.
  2. From then on, all new data were written into the attached snapshot instead of the source LUN. As a result, all daily snapshots were based on the source LUN  without  any new data refreshed. 
  3. Recently,  the old snapshot was detached and was  destroyed  after the detach operation completed. Finally, it caused data lost.
Log analysis:
  • The snapshot was created on 3th Nov 2020
A       11/03/20 19:00:04.253 SnapshotPlugin     600001 [INFO] Audit: Created snapshot UTC_2020-11-03_19:00:00 of storage resource LUN XXX
  •  It was attached to the host.
A       11/05/20 10:34:15.027 SnapshotPlugin     600005 [INFO] Audit: Attached snapshot UTC_2020-11-03_19:00:00
  • On 7th April 2021, the snapshot was detached and destroyed.
A       04/07/21 08:29:49.894 mlu               16d0007 [INFO] System: Request to detach snapshot UTC_2020-11-03_19:00:00 completed successfully.
A       04/07/21 09:58:21.585 mlu               16d0027 [INFO] System: The new name for snapshot being destroyed is Destroying_2021040709.......


Resolution

If this issue has been encountered, restore data from backup.
To avoid encountering this issue do not leave snapshot mounted to host in read/write mode

Affected Products

Dell EMC Unity
Article Properties
Article Number: 000185283
Article Type: Solution
Last Modified: 12 ديسمبر 2025
Version:  3
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