Please be aware that the content in SAP SQL Anywhere Forum will be migrated to the SAP Community in June and this forum will be retired.

We are using in our product - SA on Linux (RedHat, CentOS). Recently move from OS version 5.8 to OS version 6.4. During DB start appears follow warning -

I. 10/10 10:53:40. Running Linux 2.6.32-358.el6.x86_64 #1 SMP Fri Feb 22 00:31:26 UTC 2013 on X86_64 I. 10/10 10:53:40. Server built for X86_64 processor architecture W. 10/10 10:53:40. Direct IO disabled for file '/opt/sybase/data/db/cfg/allot_cfg.db' because transparent hugepage support is enabled and madvise is not supported

There are ways to make transparent hugepage support(THP) disable and prevent this warning ( change files /sys/kernel/mm/redhat_transparent_hugepage/enabled and /sys/kernel/mm/transparent_hugepage/defrag). Question - Should be this warning handled to prevent DB performance problem or this warning don't have influence on DB perfomance?

Thanks, HBrener

asked 13 Oct '13, 11:59

HBrener's gravatar image

accept rate: 0%

There is a bug in the Linux support for THP that causes Direct I/Os to be dropped and we have seen that this (obviously) leads to database corruption. Hence SQL Anywhere detects the situation, disables the use of Direct I/O, and issues the warning.

When SQL Anywhere is not using Direct I/O it must issue an fsync call each time that it must guarantee that the written data (in a previous write request) has hit the disk and not just buffered by the OS in memory.

Using Direct I/O is generally faster and performs better than using fsync but the exact performance impact on your application will depend on the update frequency of your application.

permanent link

answered 14 Oct '13, 03:08

Mark%20Culp's gravatar image

Mark Culp
accept rate: 41%

Your answer
toggle preview

Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here



Answers and Comments

Markdown Basics

  • *italic* or _italic_
  • **bold** or __bold__
  • link:[text]( "title")
  • image?![alt text](/path/img.jpg "title")
  • numbered list: 1. Foo 2. Bar
  • to add a line break simply add two spaces to where you would like the new line to be.
  • basic HTML tags are also supported

Question tags:


question asked: 13 Oct '13, 11:59

question was seen: 4,032 times

last updated: 14 Oct '13, 03:08