SVA - Data Migration and Increase of NCL (Net Capacity Load)

Asset ID:	1-71-1004249.1
Update Date:	2011-06-02
Keywords:

Solution Type Technical Instruction Sure

Solution 1004249.1 : SVA - Data Migration and Increase of NCL (Net Capacity Load)

Applies to:

Sun StorageTek V2X SVA Disk System - Version: Not Applicable to Not Applicable [Release: N/A to N/A]
All Platforms

Goal

Significant increase in the NCL (net capacity load) on any SVA product may occur during the migration of data. This scenario may lead to FSC 3E41 (Production Partition Conditional Capacity Low Threshold Reached) indicating less than 10% free space availability .

Solution

EXPLANATION: TDMF V1R4 (and lower releases) copies all data from tracks on a source volume, whether or not the data is associated with allocated data in the VTOC. The same result may occur with other software, depending on the parameters.

Other contributors to a high NCL may be an abundance of new data, a low compression ratio of the data, host-compressed data, and high write activity.

SOLUTION: TDMF V2R1 is enhanced to copy only the allocated or modified tracks on the source volume to the target volume. This feature will help control the NCL on the SVA.

If the source volumes are from SVA systems, then DDSR could be run on the data source subsystem prior to data migration to alleviate the problem. If the source volumes are from other subsystems, then the deleted data may still be on the volumes and will be copied.

Interval DDSR (SVAA/IXFP) is recommended to be run after data migration or full volume copies/restores. Be aware that a reserve is placed on the VTOC while Interval DDSR identifies the free space extents or deleted data. Dynamic DDSR is recommended to identify the extents as they are being deleted and does not issue a reserve.

Monitor the NCL during and after data migration to avoid FSC 3E41. The recommendation as to the maximum NCL is 75% for most workloads. Be aware that data migration and aggressive free space collection (when free space falls below 12.5%) may degrade performance.

91088
Change History
Date: 2007-10-08

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