✎ Ahsay Upgrade Advisory (#33940) - Data corruption issue on any backup types for Backup Sets upgraded to v9 (from v7 or v8 Backup Sets) [Ahsay Wiki]

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====== Ahsay Upgrade Advisory (#33940) - Data corruption issue on any backup types for Backup Sets upgraded to v9 (from v7 or v8 Backup Sets) ====== 

**Posted:** 2022-04-22

This advisory affects any legacy customer with v7 or v8 Backup Sets, who upgrade to Ahsay v9, new data backed up since v9 is unrestorable.  
On the other hand, this will not affect you if you are new to AhsayCBS v9 or created new v9 Backup Sets.

We have recently identified and confirmed a critical bug found in **AhsayCBS/OBM/ACB v9 (pre-v9.1.2.52)** that affects all types of Backup Sets, where v9 data is unrestorable (restoring data from time period prior to v9 backup dates, is restorable).

Backup users who have Backup Sets created from Ahsay v7 to v8 (agent and agentless), who upgrade to v9 are **<color #ff7f27>affected under certain conditions</color>**:
    v8 data + v9 data on CBS/OBM/ACB v9.1.0.0 to v9.1.2.51
    source files greater than 32MB
    Deduplication Migrate Data option = DISABLED
    ==> affected. Probability for data corruption for data backed up between v9.1.0.0 to v9.1.2.51

    v8 data + v9 data on CBS/OBM/ACB v9.1.0.0 to v9.1.2.51
    source files greater than 32MB
    Deduplication Migrate Data option = ENABLED
    => not affected.

    v8 data + v9 data on CBS/OBM/ACB v9.1.0.0 to v9.1.2.51
    source files less than 32MB
    Deduplication Migrate Data option = DISABLED
    => not affected.

    v8 data + v9 data on CBS/OBM/ACB v9.1.0.0 to v9.1.2.51
    source files less than 32MB
    Deduplication Migrate Data option = ENABLED
    => not affected.

    v8 data + OBM/ACB v8 on CBS v9
    => not affected. Deduplication is not applicable for v8 devices, as v8 still uses In-File Delta.

    new v9 backup set on CBS/OBM/ACB v9.x
    => not affected.


===== What does this mean? ===== 
  * On Backup Sets containing both v8 Data + v9 Data, the probability for data corruption (unrestorable data) affecting the v9 data backed up between v9.1.0.0 up to v9.1.2.51, where Deduplication //Migrate Data option// = DISABLED and source file is >32MB.

===== What happened? =====
  * After upgrading to v9 client, an internal transition (migrated) table needs to track data existing in pre-v9 backup and reference with data being backed up by v9 client. The migrate status wasn't correctly tracked for each backup file; causing the backup file to still refer to the legacy [pre-v9 data] instead of the hybrid [v9-data + pre-v9 data].

===== What are the affected CBS versions? =====
  * AhsayCBS v9.1.0.0 up to v9.1.2.51

===== Does this issue affect my customers? =====
  * Yes,  if this is true:

    v8 data + v9 data on CBS/OBM/ACB v9.1.0.0 to v9.1.2.51
    source files greater than 32MB
    Deduplication Migrate Data option = DISABLED
    ==> affected. Probability for data corruption for data backed up between v9.1.0.0 to v9.1.2.51

===== What if the setting for "Migrate Data option" changed? =====
  * This will only help for data backed up after setting is ENABLED, any v9 backup data prior to enabling this feature should be considered corrupt.
  * If this setting is later changed to DISABLED, then consider those v9 backup data after the change, corrupt; until the setting is ENABLED and jobs run.

===== What if the user's Source data is less than 32MB? =====
  * It is not affected. These source data isn't chunked for Deduplication.

===== What if the user's Source data to backup is a mix of greater-than and less-than 32MB? =====
  * It depends on the conditions stated above.

===== What action do I need to take to fix this problem? =====
  * <color #ed1c24>**Take immediate action** to download and install latest release of  **AhsayCBS v9** and **hotfix v9.1.2.52 (or higher)** via Ahsay Partner Portal (https://www.ahsay.com/partners)</color>. The latest posted hotfix is bundled with Auto Update (AUA) binaries to push the client hotfix to OBM and ACB devices when CBS AUA feature is enabled per user.
        * **UPDATE: On 2022-May-06 we released AhsayCBS v9.1.4.0; it is recommended to upgrade to this latest release as it includes prior hotfixes.**
  * Once required minimum hotfix version is applied, the next backup job will automatically first run a PDIC to handle (remove) corrupted backup file, then reupload source backup file that was corrupted and correctly update the migrate status table.

===== What if I don't want to install the hotfix, but wait for next public release? =====
  * We recommend you install the hotfix, but if you insist to delay, your alternative is to enable the //Migrate Data option//. This will only help for data backed up post-setting, any v9 data prior to enabling this feature should be considered corrupt.
  * For OBM users and Agentless clients, you can setup a new Preempted Policy, with the Deduplication enabled and marking the checkbox for "Migrate existing data to latest version". Before you decide this, ensure you understand that extra Destination storage space will be consumed, which may exceed user's storage quota. Refer to the AhsayCBS Administrator guide, and the v9 New Features Datasheet for further details about this setting.
  * For ACB users  and Agentless ACB clients, the "Migrate existing data to latest version" is found during a manual backup job. Before the user decide this, ensure understanding that extra Destination storage space will be consumed, which may exceed user's storage quota.

===== How can I purge the corrupt data? =====
  * Without installing the hotfix, as the answer may vary dependent on certain conditions, best to Contact Ahsay Support.
  * With installing the hotfix, the system will automatically run PDIC integrity check to delete affected (corrupt, orphan) data files from destination (to happen by the second weekly PDIC routine).

===== After installing the hotfix, does "Migrate Data Option" need to stay Enabled? =====
  * You can return the setting to your preference.

===== What if my maintenance has already expired? How do I upgrade? ===== 
  * **Stop! Do not upgrade** until you contact a member our Sales team [[mailto:sales-kb@ahsay.com|sales-kb@ahsay.com]] for assistance with your maintenance renewal.
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