[DOCS-1532] Don't fsync and lock secondaries during backup Created: 21/May/13  Updated: 05/Jun/13  Resolved: 05/Jun/13

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

Type: Bug Priority: Major - P3
Reporter: Nick Pellant 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, 37 weeks ago

 Description   

http://docs.mongodb.org/manual/core/backups/#replica-set-backup-considerations

The lines:
"It is possible to lock a single secondary database and then create a backup from that instance. When you unlock the database, the secondary will catch up with the primary." is incorrect as replication does not pause during a secondary being locked.

When a server is fsync and locked, reads are blocked the moment a write comes in. This is documented in SERVER-1423 with replication mentioned in SERVER-4143.

The line should, therefore, be removed. The current recommended method for doing a point in time backup is to use the --oplog option with mongodump which will provide a point in time backup similar to doing an fsync lock and unlock.



 Comments   
Comment by auto [ 05/Jun/13 ]

Author:

{u'username': u'tychoish', u'name': u'Sam Kleinman', u'email': u'samk@10gen.com'}

Message: DOCS-1532: modifying language of backup recommendation for replica sets.
Branch: master
https://github.com/mongodb/docs/commit/b9639737754d06f2461283be2db9b5481629040a

Comment by Nick Pellant [ 05/Jun/13 ]

This is assuming you're not doing a filesystem snapshot - in which case you should use fsync & lock

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