can't map area of size 0 file

[ro...@reintent.com]

Hi.

I'm having some trouble starting up my database. I shut it down properly using the shutdown command from the shell but when I start it up it's giving me this: "DBException 10446: mmap: can't map area of size 0 file: /data/test.3". There are 20 something data files for the test database. I'm not sure how/why that data file is size 0 (verified with ls).

I tried repairing and got the same error.

Any suggestions as to what I can do? Is it just a matter of removing that data file or would what cause more problems?

Thanks.

[Asya Kamsky]

Unfortunately removing the file is unlikely to make things better - frankly, given there is nothing in it, it probably won't make things worse.   I don't suppose this mongod was part of a replica set?

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[Ronak Patel]

Asya, it's not part of a replica set. Just a single node db (v2.6.4).

I moved test.3 out with no luck:

2014-12-07T08:39:20.790-0600 [initandlisten] test Assertion failure n >= 0 && n < static_cast<int>(_files.size()) src/mongo/db/storage/extent_manager.cpp 109

On Sunday, December 7, 2014 2:32:03 AM UTC-6, Asya Kamsky wrote:

Unfortunately removing the file is unlikely to make things better - frankly, given there is nothing in it, it probably won't make things worse.   I don't suppose this mongod was part of a replica set?

On Saturday, December 6, 2014, <ro...@reintent.com> wrote:

Hi.

I'm having some trouble starting up my database. I shut it down properly using the shutdown command from the shell but when I start it up it's giving me this: "DBException 10446: mmap: can't map area of size 0 file: /data/test.3". There are 20 something data files for the test database. I'm not sure how/why that data file is size 0 (verified with ls).

I tried repairing and got the same error.

Any suggestions as to what I can do? Is it just a matter of removing that data file or would what cause more problems?

Thanks.

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[Asya Kamsky]

Do you happen to have a recent backup of the files?

If there is no backup and the data is really important, it might be possible to recover some of it via mongodump --dbpath /path/to/datafiles --repair.

You might be able to get the DBs and collections that way that are in other (unharmed) data files...   

Asya

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[Ronak Patel]

Unfortunately no.

I'll give mongodump a try. Thanks.

Do you know how it would get into this state?

[Asya Kamsky]

I imagine that it would have had to be some drastic file system error/failure - once a file is allocated, mongod never truncates it to 0 as far as I know (even if everything in it is deleted, the file just remains part of the free list to be available when new data is inserted).

Maybe check various dmesg/system logs/file system logs?

Asya

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