EMC Tecnical Advisory
DiskXtender for Windows 6.1, 6.2, and 6.2 SP1: Potential Move Failure and Data Loss with Cache Moves (MediaStor, TSM, ACSLS, and NAS)
EMC issues Technical Advisories (ETA) to communicate information to customers. ETAs are articles from our Knowledgebase that address critical problems that:
- Cannot be prevented or controlled via our proactive tools and processes or
- A product defect may cause unexpected behavior or any kind of data loss.
Please read and utilize the information in this technical advisory to avoid any situation that might arise from the problem(s) described in the knowledge article. Please note that knowledge articles are updated as new information becomes available until we have a permanent solution. If you have questions regarding this advisory, please contact EMC Technical Support.
Product: DiskXtender for Windows (DXW) 6.1, 6.2, and 6.2 SP1 (Note: This ETA is NOT applicable for Centera media)
Impact: Potential DL
Symptoms
Small groups of data within the same date range have migration information; however, no trace of the data is found on the backend media.
The extent of the exposure can be determined using the appropriate utility to verify the media:
- DxNasVerify for NAS media
- DxTSMVerify for TSM media
There are no verification tools for ACSLS or MediaStor media services. You must manually run Media File Reports to determine if files exist on media as they are discovered on the extended drive.
Issue
If a file experiences an error during write, while using the cached moves feature to queue small batches of files for migration in DXW 6.1, 6.2, and 6.2 SP1, DXW properly considers this file to be a non-migrated file. However, the files in the queue that were written prior to the file that failed are considered migrated, but the data does not exist on the backend. The queue of files in the cached move is a small subset of the move list. The cached moves feature is enabled by default. The following media services are affected: MediaStor, TSM, ACSLS, and NAS. This does not affect Centera media services.
Resolution
Upgrade to 6.3 (which does not have this issue)
Upgrade to the patch revision that fixes this issue:
- For version 6.1 - customers must upgrade to patch 10 (DXW_Fsm610040-Patch10) or greater
- For version 6.2 - customers must upgrade to 6.2 SP1 and then apply patch 3 or greater
- For version 6.2 SP1 - customers must upgrade to patch 3 (DXW_Fsm620090-Patch3) or greater
- Workaround: Disable the cached moves feature (which is enabled by default) by changing the "Cached moves file watermark" to "1" (one). This setting is found in the Media Group Properties dialog box > Options tab. This will eliminate the exposure to data loss if an error occurs during migration but may impact performance for migration.
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