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Linux: eloqdb6 causes system delay


Title: Linux: eloqdb6 causes system delay
Document: 918695244
Author: Michael Marxmeier (mike@msede.com)
Keywords: eloqdb6,Linux,A0600,sync

Q: When using sync write mode (default with A.06.20) my Linux server seems to stall every minute.

A: This is caused by an issue of the Linux kernel syncing large files (with the ext2 file system).

When the eloqdb6 performs in sync write mode (default as of A.06.20) a fsync() on the data volume(s) is performed during checkpoint operation (every minute by default).

The algorithm used by the ext2 filesystem for syncing buffers to disk is inefficient for big files (this is a know problem but not easy to change). When using the eloqdb6 in sync write mode (which is the default now) this may cause delays and the system may seem to stall for a few seconds when eloqdb6 performs a checkpoint operation (default every 60 seconds). This gets noticeable when the database volume files grow beyound 100 MB and gets worse the bigger the files get.

A kernel patch is available as a workaround. For more information please refer to the A.06.20 Release Notes.

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