Chapter 8. Troubleshooting Compressed File Systems; Recovery Scenario: Allocated Capacity Exceeds Capacity Threshold - IBM Storwize V7000 Unified Problem Determination Manual

Chapter 8. Troubleshooting compressed file systems

to ensure that the capacity demands are not exceeded, the underlying block storage
pools that provide the compression mechanism for file systems need to be
monitored and maintained.
When a block storage pool that is used for compressed file systems runs out of
capacity, any compressed volume using that pool that expands is taken offline. If a
volume used by a file system is offline for more than 30 seconds then the file
system is unmounted, and all I/O to the file system fails. This behavior is different
from file systems. When a file system runs out of capacity, the file system enters
read-only mode.
To ensure that capacity demands are met for a compressed file systems, monitor
capacity usage for the block storage pools and volumes that provide the
underlying compression mechanism for file systems. For details on setting
thresholds and monitoring capacity for both the block storage and compressed file
systems, see "Monitoring file system compression" on page 303
However, there can be cases where capacity exceeds the demands of the data being
compressed and additional capacity needs to be added to the system. The
following table provides an overview of typical recovery scenarios that are related
to running out of capacity for compressed file systems.

Recovery scenario: Allocated capacity exceeds capacity threshold

If the allocated capacity of the block storage pool exceeds the specified capacity
threshold then its compressed volumes can go offline. The default threshold is 80%
of capacity; however, the value can be set lower or higher depending on the
environment. If a compressed file volume is offline for 30 seconds, the file system
is unmounted. Proper monitoring of storage pool thresholds is essential to ensure
capacity consumption is not exceeding expectations. If the used capacity does
exceed the specified threshold, you can recover by adding more storage to the
block storage pool or delete data to free up space in the file system.
The most important metric to monitor is the physical capacity that is used in the
storage pool. Make sure the physical allocation does not exceed the specified
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Table 45. Capacity recovery scenarios
Recovery Scenario
Storage pool warning indicates the pool is at
the specified capacity threshold. The default
threshold is 80%.
Estimate compression savings for file system
in not achieved. (File system is still online)
Storage pool is full and the file system pool
is offline.
Storage pool is full and the file system pool
is offline, but no additional storage is
available to add to the pool.
Recovery Procedure
Increase capacity of the storage pool.
One of these options:
1. Increase capacity of the storage pool.
2. Reduce the capacity of the file system.
Increase capacity of the storage pool.
Contact IBM Remote Technical Support or
your service representative.
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