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Why does flex volume clone split take a long time?

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Applies to

Data ONTAP 7 and earlier

Answer

Flex Volume Clone split of 140G volume is running for over 18hrs and is not yet complete

Why flex volume clone split take a long time

FlexClone split process is slow

The clone-splitting operation, in general, might take considerable time to carry.

Analyzing the stats show -n output of the volumes involved in flex vol clone split process will show that the flex clone is a clone of the actual volume and it does not matter how full the volume is.

The flex clone split has to transfer every bit of data and free inode to the volume that is being cloned.
Hence, when a split is done, the total number of inodes displayed is used plus free and each is copied to the volume that is being split and separated from the source.

The clone-splitting operation is a copy operation that might take considerable time and resources to carry out because of the following reasons:

  • Free blocks in the aggregate are used to copy blocks shared between the parent and the clone.
  • FlexClone splitting incurs disk I/O operations, and can potentially compete with other disk operations in the aggregate.
  • Copy operation uses some CPU and memory resources, which may impact the performance of a fully-loaded filer.

However, Data ONTAP addresses the potential performance impact of the Split operation. The Split operation runs in the background, and priorities are set in such a way that it does not significantly impact foreground operations. Data ONTAP also provides commands to stop or check the status of a clone-splitting operation such as vol clone stop cl_vol_name and vol clone status cl_vol_name . See this for more on: how to split a clone from its parent volume.

The clone operation proceeds in the background and does not interfere with data access to either the parent or the clone volume. Also, the user processes are not affected during the operation and the split operation is treated as a low priority job. This is not like a volume copy operation that copies only the data written in the volume.

If you create a clone volume, you can immediately start to use it and allow the split to occur in the background without impact to the data integrity (other than the fact that a snapshot cannot occur until the split completes). For more information about Cloning flexible volumes, refer Data ONTAP™ 7.0 Storage Management Guide.

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