Thin-provisioned FlashCopy

You can have a mix of thin-provisioned and standard-provisioned volumes in FlashCopy® mappings. One common combination is a standard-provisioned source with a thin-provisioned target, which enables the target to consume a smaller amount of real storage than the source.

For best performance, the grain size of the thin-provisioned volume must match the grain size of the FlashCopy mapping. However, if the grain sizes are different, the mapping still proceeds.

When you create your FlashCopymappings, consider the following information:

• If you are using a standard-provisioned source with a thin-provisioned target, disable background copy and cleaning mode on the FlashCopy map by setting both the background copy rate and cleaning rate to zero. Otherwise, if these features are enabled, all the source is copied onto the target volume. This action causes the thin-provisioned volume to either go offline or to grow as large as the source.
• If you are using only thin-provisioned source, only the space that is used on the source volume is copied to the target volume. For example, if the source volume has a virtual size of 800 GB and a real size of 100 GB of which 50 GB is used, only the used 50 GB are copied.
• A FlashCopy bitmap contains 1 bit for every grain on a volume. For example, if you have a thin-provisioned volume with 1 TB virtual size (100 MB real capacity), you must have a FlashCopy bitmap to cover the 1 TB virtual size even though only 100 MB of real capacity is allocated.