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26 Chapter 2 Overview of CCI Operations
2.4.2.2 Hitachi TrueCopy Asynchronous Transition States
Hitachi TrueCopy Async volumes have special states for sidefile control during status
transitions. Table 2.6 shows the transition states f
or Hitachi TrueCopy Synchronous and
Hitachi TrueCopy Asynchronous volumes.
The suspending and deleting states are temporary internal states within the RAID storage
system. CCI cannot detect these transition states, because these states are reported on the
previous state from the storage system. These states are therefore concealed inside the
pairsplit command. After the pairsplit command is accepted, host write I/Os for the P-VOL
are managed by the cylinder bitmap (normal), non-transmitted data remaining in the
P-VOL’s FIFO queue is transferred to the S-VOL’s FIFO queue, and the pair status is then set
to PSUS [SMPL] state when all data in the P-VOL’s FIFO queue has been transmitted.
PFUL. If the quantity of data in sidefile cache exceeds 30% of cache storage, the internal
status of the RAID storage system is PFUL, and host write I/Os receive delayed response in
the range of 0.5 seconds to 4 seconds.
PFUS. If the quantity of data in sidefile cache exceeds the user-defined sidefile area (30%–
70%), then host write I/Os are waited for enough sidefile space to store the next new write
data. If the copy pending timeout occurs during this waiting state, then the pair status
changes from PAIR to PFUS, host write I/Os are accepted, and write data is managed by
bitmap.
The CCI software can detect and report the PFUL and PFUS states as follows:
As a return code of the pairvolchk command
As the status code displayed to code item by the pairmon command
As the paired status displayed to status item using -fc option of pairdisplay command