506 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
10.3.11 FlashCopy mapping states
This section describes the states of a FlashCopy mapping.
Idle_or_copied
The source and target volumes act as independent volumes even if a mapping exists between
the two. Read and write caching is enabled for the source and the target volumes.
If the mapping is incremental and the background copy is complete, the mapping records the
differences between the source and target volumes only. If the connection to both nodes in
the I/O group that the mapping is assigned to is lost, the source and target volumes are
offline.
Copying
The copy is in progress. Read and write caching is enabled on the source and the target
volumes.
Prepared
The mapping is ready to start. The target volume is online, but is not accessible. The target
volume cannot perform read or write caching. Read and write caching is failed by the Small
Computer System Interface (SCSI) front end as a hardware error. If the mapping is
incremental and a previous mapping is completed, the mapping records the differences
between the source and target volumes only. If the connection to both nodes in the I/O group
that the mapping is assigned to is lost, the source and target volumes go offline.
Preparing
The target volume is online, but not accessible. The target volume cannot perform read or
write caching. Read and write caching is failed by the SCSI front end as a hardware error. Any
changed write data for the source volume is flushed from the cache. Any read or write data for
the target volume is discarded from the cache.
If the mapping is incremental and a previous mapping is completed, the mapping records the
differences between the source and target volumes only. If the connection to both nodes in
the I/O group that the mapping is assigned to is lost, the source and target volumes go offline.
Performing the cache flush that is required as part of the startfcmap or startfcconsistgrp
command causes I/Os to be delayed while they are waiting for the cache flush to complete. To
overcome this problem, FlashCopy supports the prestartfcmap or prestartfcconsistgrp
commands, which prepare for a FlashCopy start while still allowing I/Os to continue to the
source volume.
In the Preparing state, the FlashCopy mapping is prepared by completing the following steps:
1. Flushing any modified write data that is associated with the source volume from the cache.
Read data for the source is left in the cache.
2. Placing the cache for the source volume into write-through mode so that subsequent
writes wait until data is written to disk before the write command that is received from the
host is complete.
3. Discarding any read or write data that is associated with the target volume from the cache.
To Next Page
Loading...
Need help?
General