Administrator Guide

CAUTION: Performing a major host operation (such as a LIP reset, for example) in order to detect a change in
volume size presents risk to volumes accessed by the host. It is best to avoid such resource intensive operations
during volume expansion.
● Expansion initialization traffic occurs on disk areas that are not performing host I/O. In addition, the amount
of time taken to initialize the newly added capacity depends on the performance of the array hosting that
is the storage volumes. However, the expected performance is still faster than the time taken to rebuild a
volume.
● Across distributed RAID 1 devices, the initialization process does not consume WAN data bandwidth as each
cluster performs its initialization locally.
● On RAID 1 and distributed RAID 1 devices, metro node ensures that all RAID 1 legs have consistent
information on the expanded space.
● The level of redundancy on RAID 1 and distributed RAID 1 device geometries is maintained through the
expansion and initialization process.
● The newly expanded virtual volume capacity will be available to use by hosts when the initialization process
has finished.
● If metro node has claimed the storage volumes as thinly provisioned, the initialization process will not affect
the underlying provisioning of the additional capacity reported to metro node.
Check status of volume expansion
Query the status of your volume expansion by listing the value of the following attributes in the virtual-volumes context.
● expansion-status - Status of virtual volume expansion. Indicates whether a virtual volume expansion is underway or has
failed.
The attribute will have one of the following values:
○ in-progress - Expansion is in progress.
○ failed - Most recent in-progress expansion has failed and expansion needs to be retried. If expansion is not retried,
then this state persists for up to two days. If two days pass with no fix, the failed state clears and the volume is assumed
fixed.
○ unknown - Status cannot be determined. This may be because of a communication error or because of an internal
programming error.
○ - (dash character) - None of the above states apply.
● expansion-summary - If there are no in-progess or failed expansions, and no virtual volumes with a non-zero expandable-
capacity, then the virtual volume summary command displays No expansion activity in expansion-summary.
Limitations
The following are general limitations for expanding virtual volumes.
Some virtual volumes cannot be expanded under specific circumstances. Volumes cannot be expanded if any of the following
conditions are true:
● Migration or rebuilding is occurring - Expansion is blocked during migration or rebuilds.
○ If you are rebuilding volumes, wait until the rebuild is complete before attempting expansion.
○ If you are migrating data, wait until the migration is complete. Alternatively, cancel or commit the migration, and then
perform the expansion.
● Upgrade is occurring - Volume expansion is blocked during Non-Disruptive Upgrade (NDU).
● health-check command reports problems - The health-check command returns problems relating to the cluster,
storage volumes, or virtual volume being expanded.
● Volume is a metadata volume - Metadata volumes cannot be expanded.
Volume expansion
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