[DOCS-28] Clarify what can be lost on a server crash Created: 12/Jun/10  Updated: 15/Aug/11  Resolved: 13/Jun/10

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

Type: Improvement Priority: Major - P3
Reporter: Karoly Negyesi Assignee: Unassigned
Resolution: Done Votes: 1
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:
Days since reply: 13 years, 36 weeks, 4 days ago

 Description   

It is not clear entirely what can be lost in case of a mongod crash – is it just the unwritten data or is it possible to lose already written data too? It's not clear from http://www.mongodb.org/display/DOCS/Durability+and+Repair



 Comments   
Comment by Karoly Negyesi [ 12/Jun/10 ]

I have changed the page per Eliot's comment. This ticket now can be closed.

Comment by Eliot Horowitz (Inactive) [ 12/Jun/10 ]

Will let kyle fix the website, but the answers below.

On a mongod crash, only the last few second should be lost.
The system will still flush other changes.

On a system crash or power outage, there is potential to lose anything.
In practice its rare to lose more than a few seconds, but possible.

1.8 will have full durability.
see: SERVER-980

Comment by Richard Clark [ 12/Jun/10 ]

Specifically, we're interested both in what can happen if mongo crashes yet the system continues to run, and what happens if the system dies from a power outage. The question arises due to anecdotal evidence that suggests that more than just the last few records disappear under certain circumstances, specifically large update operations.

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