Flashes (Alerts)
Abstract
IBM has identified an issue in IBM Spectrum Scale V4.2.0.0 through 4.2.3.21 (ESS 4.0 through ESS 5.2.9), or V5.0.0.0 through 5.0.4.3 levels (ESS 5.3 through ESS 5.3.5.2 or ESS 6.0.0.0 through ESS 6.0.0.2), in which undetected data corruption may occur for data being written with small sequential write (non-direct I/O) operations, while a file is being concurrently compressed or decompressed.
Content
Issue:
With sequential write (non-direct I/O) operations of size less than half a file system data block size, the cached fast write code path could be enabled. While a file is being compressed or decompressed, data written to the same file by a concurrent cached fast write may be lost.
Users Affected:
This issue may affect customers running any level of IBM Spectrum Scale (GPFS) V4.2.0.0 through 4.2.3.21 (ESS 4.0 through ESS 5.2.9), or V5.0.0.0 through 5.0.4.3 (ESS 5.3 through ESS ESS 5.3.5.2 or ESS 6.0.0.0 through ESS 6.0.0.2), when they use the file compression functionality, and applications perform small sequential writes.
Users may be affected only when all of the following conditions are met:
- The Spectrum Scale (GPFS) compression functionality is being used.
- Applications perform sequential I/O writes of size less than half of the file system data block size.
- The write operation is not doing direct I/O. That is, the O_DIRECT flag is not used when the file is opened.
- The file is not memory-mapped.
Problem Determination:
There are no external indicators that this problem may be occurring — no error message is produced by Spectrum Scale. The only indication of the problem is that applications may experience incorrect data being returned (missed updates).
Recommendation:
1.) Users running IBM Spectrum Scale V5.0.0.0 through V5.0.4.3 (ESS 5.3 through ESS 5.3.5.2 or ESS 6.0.0.0 through ESS 6.0.0.2) levels should apply IBM Spectrum Scale V5.0.4.4 or later.
2.) Users running IBM Spectrum Scale V4.2.0.0 through V4.2.3.21 (ESS 4.0 through ESS 5.2.9) levels should apply IBM Spectrum Scale V4.2.3.22 (ESS 5.2.10) or later
3.) If you cannot apply one of the above PTF levels, contact IBM service to obtain and apply an efix for your code level(s):
- For IBM Spectrum Scale V5.0.0.0 through 5.0.4.3, reference APAR IJ24455
- For IBM Spectrum Scale V4.2.0.0 through 4.2.3.21, reference APAR IJ24581
4.) Until the fix is applied, users should temporarily stop using the Spectrum Scale compression functionality, wherever the above listed conditions may be met.
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Document Information
Modified date:
05 August 2020
UID
ibm16220548