IBM Spectrum Scale (GPFS): Asynchronous I/O write: file size change may not be updated

Content

Problem Summary:

As a result of an asynchronous Direct I/O write using the io_ submit interface, file size change may not be updated correctly, leading to possible undetected loss of data when a node fails before file size change is committed to disk.

Users affected:

Users running IBM GPFS V4.1.0.4 through V4.1.0.8, IBM Spectrum Scale V4.1.1 through V4.1.1.14, or IBM Spectrum Scale V4.2.0.0 through V4.2.3.0 on LINUX and using asynchronous Direct I/O via the io_submit interface. Applications using only Posix asynchronous Direct I/O will not experience the problem. The following conditions must all exist in order for the problem to occur:

1. Application performs multiple asynchronous Direct I/O writes from the same node via the io_submit interface.

2. Writes to the end of data file that will cause an increase in the file size.

3. Size of the writes must be less than full GPFS data block.

4. Node failure occurs shortly after writes finish and before file size update is committed to disk.

Recommendations:

1. Any customer using affected code levels (IBM GPFS 4.1.0.4 through V4.1.0.8, IBM Spectrum Scale V4.1.1 through 4.1.1.14, or IBM Spectrum Scale 4.2.0.0 through 4.2.3.0) should either (a) Stop using io_submit for asynchronous Direct I/O to perform write; (b) Disable Linux asynchronous file sync via GFFS command: "mmchconfig enableLinuxAioFsync=false"; or (c) wait until they are able to apply the fix pack or an efix by contacting IBM Service:

For IBM Spectrum Scale V4.2.0.0 thru V4.2.3.0, apply V4.2.3.1, or reference APAR IV95925.

For IBM Spectrum Scale V4.1.1.0 thru V4.1.1.14, apply V4.1.1.15, or reference APAR IV95929.

For IBM GPFS V4.1.0.4 thru V4.1.0.8, reference APAR IV95929.

IBM Spectrum Scale V4.2.3.1 can be downloaded from Fix Central at https://www-945.ibm.com/support/fixcentral/swg/selectFixes?parent=Software%20defined%20storage&product=ibm/StorageSoftware/IBM+Spectrum+Scale&release=4.2.3&platform=All&function=all

IBM Spectrum Scale V4.1.1.15 can be downloaded from Fix Central at https://www-945.ibm.com/support/fixcentral/swg/selectFixes?parent=Software%20defined%20storage&product=ibm/StorageSoftware/IBM+Spectrum+Scale&release=4.1.1&platform=All&function=all

2. If you believe that your GPFS file system may be affected by this issue, you should contact IBM Service as soon as possible for further guidance and assistance.