IBM TS7700 Series, Руководство пользователя

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August 15, 2017
© Copyright IBM Corporation, 2017 Page 27 of 117
Note: It is possible that if enough logical volumes had been only in cache at the start of the operation, a few
additional physical volumes will be used during the export operation and that may result in slightly more
than 2000 volumes total that have been exported. Even though the number of copy exported volumes
exceeds 2000, the copy export operation will continue execution, but subsequent copy export operations will
fail until the number of volumes is again under the limit. At code release level R1.6 and higher, the 2000
volume limit can be changed to a maximum of 10000.
The export operation then continues processing as follows:
•
The TS7700 determines the logical volumes to be exported. When the operation begins, a logical
volume must:
•
Be assigned to the management class that defined the secondary physical volume pool specified in
the export list file
•
Must have a valid copy of the volume resident in the TS7700. A logical volume does not have to be
actually on one of the physical volumes in the pool at the beginning of the operation to be
considered, it can be resident only in the cache. In a Grid configuration, if the volume’s copy policy
specified that it is to have a copy on the TS7700 performing the export, but the copy had not
completed when the operation began, it is not considered for export during the operation.
•
If the volume is only in the cache, it must be scheduled to be copied to the secondary physical
volume pool. When a volume is closed it is checked to determine whether it had been written to. If
that was the case, it is added to the queue for copying to the physical volume pools defined by the
volume’s storage group and management class storage constructs associated with the volume.
•
At code release level R3.2 or higher, if Time Delayed Premigration is applied to a logical volume by
the volume’s storage class associated with it, the logical volume is not added to the queue for
copying to the physical volume pools and keeps resident state until configured Premigration Delay
Time has passed since its Premigration Delay Reference time (Volume Creation time or Volume
Last Accessed time). This means that logical volumes to which Time Delayed Premigration is
applied and whose Premigration Delay Time has not passed yet can’t be candidates to be exported
even if their secondary pool is configured as copy export pool. This is a point which should be kept
in mind.
Note: At code release level R2.0 and lower, if a mount request is processed for a volume that is queued
to be copied to a physical volume pool, it is removed from the queue as part of mount processing. It is
not automatically requeued when the volume is closed if it was only read while mounted. It will be
requeued as part of a background process that scans the cache looking for cache-resident only volumes
that need to be copied to their physical volume pool(s). The background process runs approximately
every 4 hours. This means that it is possible for a volume to be resident in the cache, associated with the
secondary physical volume pool to be exported and not be considered for the export operation because it
had been removed from the queue. It would be eligible for a subsequent copy export operation once it
had been requeued. At code release level R2.1 and higher, a volume queued to be copied to a physical
volume pool is not removed from the queue by mount processing for only reading.
Logical volumes assigned to the secondary physical volume pool after the operation begins or those that
do not have a valid copy resident in the TS7700 are not considered (they could be considered in a
subsequent copy export operation). Also, if a physical volume in the specified secondary physical
volume pool contains one or more primary copies of logical volumes or the volume is written in a pre-
TS7700 format, that physical volume and any logical volumes on it are not considered for export. If a
logical volume meets some, but not all of the criteria to be exported during the operation, those volumes