[DOCS-1245] Misleading comment saying point-in-time snapshop is impossible with mongodump Created: 16/Mar/13  Updated: 03/Nov/17  Resolved: 16/Jan/14

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

Type: Improvement Priority: Major - P3
Reporter: Michael C. Harris Assignee: Unassigned
Resolution: Done Votes: 0
Labels: collector-298ba4e7
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified
Environment:

Location: http://docs.mongodb.org/manual/administration/backups/
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.22 (KHTML, like Gecko) Chrome/25.0.1364.172 Safari/537.22
Referrer: http://docs.mongodb.org/manual/contents/
Screen Resolution: 1920 x 1080
repo: docs
source: administration/backups


Participants:
Days since reply: 10 years, 4 weeks, 6 days ago

 Description   

binary database dumps are comparatively small, because they don’t include index content or pre-allocated free space, and record padding. However, it’s impossible to capture a copy of a running system that reflects a single moment in time using a binary dump.

Point-in-time snapshots are possible using mongodump --oplog (since 1.7.4) if the instance is running as part of a replica set.

Both methodologies have advantages and disadvantages

Even if my assertion above is shown to be incorrect, only a single disadvantage is listed for each strategy.



 Comments   
Comment by Kay Kim (Inactive) [ 16/Jan/14 ]

Closing as the backup strategy page underwent significant rewrite

Comment by Michael C. Harris [ 17/Mar/13 ]

Thanks, I'll expand to include --oplogReplay and mention time.

it definitely doesn't work in the sharded case.

Do you mean because of the difficulty of synchronising backups across nodes? If so, that's an issue that's not restricted to binary dumps. I'll move point-in-time snapshots to another paragraph, it's becoming clunky in the list.

Comment by Sam Kleinman (Inactive) [ 17/Mar/13 ]

-oplog helps (when used with {{-oplogReplay)), but the problem is less in the single-member or single replica-set case, it definitely doesn't work in the sharded case.

I'll get someone else with more backup experience than I have to look this over, but I think it would be good to:

  • add notes about --oplogReplay, and
  • mention that mongodump/mongorestores take longer to complete (in general.)
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