Bad performance in SAN environment for append AIO

Solution Verified - Updated -

Issue

Because SAP recommends to use dft_extent_sz, which is set to 2 (2 pages for 16K each), any DB2 object is expanded exactly to 32k and on bulk inserts leads to exactly 32k append AIO, which doesn't perform as expected.

Environment

  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • sysbench IO tool from EPEL
  • Ext-4 filesystem

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