[SERVER-26743] Have a pre-allocated "crash zone" file to more gracefully handle out of disk scenarios Created: 24/Oct/16  Updated: 24/Oct/16  Resolved: 24/Oct/16

Status: Closed
Project: Core Server
Component/s: Storage
Affects Version/s: None
Fix Version/s: None

Type: New Feature Priority: Minor - P4
Reporter: Rod Adams Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Duplicate
duplicates SERVER-18025 Option to allocate disk space headroo... Closed
Participants:

 Description   

Of late, we've had a rash of customer run out of disk space, and then have to perform resyncs or other actions to make their instance consistent again after freeing up some empty space.

What if we made an option to pre-allocate a 2-3G "crash pad" file, which when we experience an out of disk scenario, we can steer records of the writes we'd like to have done into that file, and then crash, with an intention of being able to restart later on, and replay the missed writes, returning us to a consistent state.

This is very similar to regular journalling, but the key difference would be that the space is pre-allocated, so would be able to work around running out of space.

I've left out ~1000 implementation details I haven't worked out, mainly just noting the general thought.



 Comments   
Comment by Rod Adams [ 24/Oct/16 ]

That it does.
Cool.

Comment by Ramon Fernandez Marina [ 24/Oct/16 ]

This looks like a duplicate of SERVER-18025.

Comment by Rod Adams [ 24/Oct/16 ]

Excellent question. I know we've had a lot of cases like this of late (these things come in waves), but I'll have to track down if it's all MMAP, and/or some other piece. I'll get back to you.

Comment by Eric Milkie [ 24/Oct/16 ]

Do you need to resync WiredTiger nodes when they run out of disk space, or does this only affect mmap?

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