[DOCS-1416] --journalCommitInterval default value misleading Created: 20/Apr/13  Updated: 30/Oct/23  Resolved: 24/Apr/13

Status: Closed
Project: Documentation
Component/s: manual
Affects Version/s: None
Fix Version/s: Server_Docs_20231030

Type: Task Priority: Major - P3
Reporter: J Rassi Assignee: Sam Kleinman (Inactive)
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:
Days since reply: 10 years, 43 weeks ago

 Description   

The default for the mongod option --journalCommitInterval is either 30ms or 100ms, depending on your system configuration (see code). The documentation as it exists currently is misleading. Each of the following could at least use a footnote to that end:

source/core/journaling.txt:100 milliseconds.
source/core/journaling.txt:group commits. By default, MongoDB performs a group commit every 100
source/core/journaling.txt:milliseconds: as a result MongoDB commits all operations within a 100
source/core/write-operations.txt:  fundamental basis for write concern, there is an up-to 100
source/faq/developers.txt:every 60 seconds and commits the :term:`journal` every 100
source/faq/fundamentals.txt:Writes are physically written to the :doc:`journal </core/journaling>` within 100
source/reference/configuration-options.txt:   *Default:* 100
source/reference/configuration-options.txt:   value is 100 milliseconds. Lower values increase the durability of
source/reference/glossary.txt:      100ms and this is configurable using the
source/reference/mongod.txt:   between journal operations. The default value is 100 milliseconds,
source/release-notes/2.0.txt:  specifying your own group commit interval. 100ms is the default (same as
source/tutorial/recover-data-following-unexpected-shutdown.txt:<setting-journal>`. The journal writes data to disk every 100



 Comments   
Comment by auto [ 24/Apr/13 ]

Author:

{u'date': u'2013-04-24T13:31:13Z', u'name': u'Sam Kleinman', u'email': u'samk@10gen.com'}

Message: DOCS-1416 additional corrections
Branch: v2.2
https://github.com/mongodb/docs/commit/56796a29c7e6970e27bc2ee25393697019980fc1

Comment by auto [ 24/Apr/13 ]

Author:

{u'date': u'2013-04-24T13:31:13Z', u'name': u'Sam Kleinman', u'email': u'samk@10gen.com'}

Message: DOCS-1416 additional corrections
Branch: master
https://github.com/mongodb/docs/commit/6d92d762043138a2048a3679b54ca530b78c1c7c

Comment by J Rassi [ 20/Apr/13 ]

The commit interval default will be 100ms if the containing filesystem for the data directory is associated with the same block device as the containing filesystem for the journal directory. Otherwise, it will be 30ms.

("Partition" is a misnomer in the code here – the correctness of that term breaks down, for example, if you're running off a single disk that isn't partitioned at all, or if you have LVM configured to run data/journal off of separate logical volumes backed by a device associated with a single disk partition)

Comment by Ed Costello [ 20/Apr/13 ]

Could you confirm that the decision for 30 vs 100ms is based on whether the journal is on the same partition as (I'm guessing, I didn't read too far back in the code) the database files?

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