How TrueCopy works
A pair is created when you:
Select a volume on the primary storage system that you want to copy.
Create or identify the volume on the secondary system that will contain the copy.
Connect the primary and secondary storage systems with a Fibre Channel channel data path.
Copy all primary system data to the secondary volume.
During a typical initial copy, all data written to the primary volume (P-VOL) is copied to the secondary volume (S-VOL), ensuring that the secondary copy is a complete and consistent backup.
When a pair is split, writes to the P-VOL continue but are no longer copied to the S-VOL, and the pair is no longer synchronized.
You can enable read and write access from the secondary host to an S-VOL as a pair is split.
Changes to P-VOL and S-VOL (if applicable) are tracked by differential bitmaps until the pair is resynchronized.
When resynchronization takes place, only the changed data is transferred, reducing copy time.
The Hitachi Virtual Storage Platform G200, G400, G600 transfers control parameters and FBA-format data for consecutive, updated records in a track using a single write operation. This eliminates the overhead that is usually required for performing FBA-to-CKD and CKD-to-FBA conversions.
To plan and implement a TrueCopy system an understanding of its components is required. For this and all planning information and requirements, see the Hitachi TrueCopy® User Guide.