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In an IBM Spectrum Scale V4.2 file system with multiple storage pools, Quality of Service settings should be set for all storage pools

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Abstract

In an IBM Spectrum Scale V4.2 file system with multiple storage pools, Quality of Service (QoS) settings should be set for all storage pools to avoid performance degradation for unspecified storage pools.

Content


Problem Summary:
In an IBM Spectrum Scale V4.2 file system with multiple storage pools, if the user specifies Quality of Service for I/O operations (QoS) settings (for the maintenance and other classes) only for one storage pool then the I/O allocations for the unspecified pools will be set to a very low value, resulting in severe performance degradation when I/O is performed to the unspecified storage pool(s).

Users Affected:
This issue affects all IBM Spectrum Scale V4.2 users who utilize both multiple storage pools and the Quality of Service function.


Recommendation:
Until an efix is available with APAR IV79188, specify the QoS settings for all the pools when issuing the mmchqos command for a given file system. For example, if you have a system pool and a poolx, for the file system fs2, you would issue:

mmchqos fs2 --enable pool=poolX,other=inf,maintenance=2000IOPS pool=system,other=inf,maintenance=inf

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Document Information

Modified date:
25 September 2022

UID

ssg1S1005464