On a 174G mongo db with less than 5G space left on disk:
> db.174GrunCommand(

)

Thu Feb 28 15:04:57 [FileAllocator] allocating new datafile /srv/mongodb/logs.101, filling with zeroes...
Thu Feb 28 15:04:57 [FileAllocator] FileAllocator: posix_fallocate failed: errno:28 No space left on device falling back
Thu Feb 28 15:04:59 [FileAllocator] error: failed to allocate new file: /srv/mongodb/logs.101 size: 536608768 failure creating new datafile; lseek failed for fd 228 with errno: errno:28 No space left on device. will try again in 10 seconds
Thu Feb 28 15:05:02 [initandlisten] connection accepted from 163.5.68.53:52434 #124 (117 connections now open)
Thu Feb 28 15:05:03 [conn29] LogFile::synchronousAppend failed with 5300224 bytes unwritten out of 5300224 bytes; b=0x7f51129a8000 errno:28 No space left on device
Thu Feb 28 15:05:03 [conn29] logs.info Fatal Assertion 13515
0xb07561 0xacc8b3 0xae4b3f 0x73b215 0x73b442 0x73104b 0x73157a 0x72ef8c 0x72f09c 0x57cb06 0x57ecdd 0x57fb47 0x582cf0 0x6e8e51 0x6ea6c2 0x6eb67c 0x837468 0x83abb0 0x7b0afd 0x7b3e23
/usr/local/mongodb-current/bin/mongod(_ZN5mongo15printStackTraceERSo+0x21) [0xb07561]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo13fassertFailedEi+0xa3) [0xacc8b3]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo7LogFile17synchronousAppendEPKvm+0x14f) [0xae4b3f]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur7Journal7journalERKNS0_11JSectHeaderERKNS_14AlignedBuilderE+0x1e5) [0x73b215]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur14WRITETOJOURNALENS0_11JSectHeaderERNS_14AlignedBuilderE+0x32) [0x73b442]
/usr/local/mongodb-current/bin/mongod() [0x73104b]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur11DurableImpl9commitNowEv+0x1a) [0x73157a]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur11DurableImpl16_aCommitIsNeededEv+0x14c) [0x72ef8c]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur11DurableImpl14commitIfNeededEb+0x4c) [0x72f09c]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo13compactExtentEPKcPNS_16NamespaceDetailsENS_7DiskLocEiRKN5boost12scoped_arrayINS_9IndexSpecEEERNS6_INS_12SortPhaseOneEEEibdi+0x516) [0x57cb06]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo8_compactEPKcPNS_16NamespaceDetailsERSsbRNS_14BSONObjBuilderEdi+0x142d) [0x57ecdd]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo7compactERKSsRSsbRNS_14BSONObjBuilderEdi+0x277) [0x57fb47]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo10CompactCmd3runERKSsRNS_7BSONObjEiRSsRNS_14BSONObjBuilderEb+0x950) [0x582cf0]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo12_execCommandEPNS_7CommandERKSsRNS_7BSONObjEiRNS_14BSONObjBuilderEb+0x51) [0x6e8e51]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo11execCommandEPNS_7CommandERNS_6ClientEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb+0xd52) [0x6ea6c2]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo12_runCommandsEPKcRNS_7BSONObjERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi+0x2ac) [0x6eb67c]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo11runCommandsEPKcRNS_7BSONObjERNS_5CurOpERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi+0x38) [0x837468]
/usr/local/mongodb-current/bin/mongod(ZN5mongo8runQueryERNS_7MessageERNS_12QueryMessageERNS_5CurOpES1+0xc10) [0x83abb0]
/usr/local/mongodb-current/bin/mongod() [0x7b0afd]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_11HostAndPortE+0x3a3) [0x7b3e23]
Thu Feb 28 15:05:03 [conn29]

***aborting after fassert() failure

Thu Feb 28 15:05:03 Got signal: 6 (Aborted).

Thu Feb 28 15:05:03 Backtrace:
0xb07561 0x5598c9 0x7fa31af36230 0x7fa31af361b5 0x7fa31af38fc0 0xacc8ee 0xae4b3f 0x73b215 0x73b442 0x73104b 0x73157a 0x72ef8c 0x72f09c 0x57cb06 0x57ecdd 0x57fb47 0x582cf0 0x6e8e51 0x6ea6c2 0x6eb67c
/usr/local/mongodb-current/bin/mongod(_ZN5mongo15printStackTraceERSo+0x21) [0xb07561]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo10abruptQuitEi+0x399) [0x5598c9]
/lib/libc.so.6(+0x32230) [0x7fa31af36230]
/lib/libc.so.6(gsignal+0x35) [0x7fa31af361b5]
/lib/libc.so.6(abort+0x180) [0x7fa31af38fc0]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo13fassertFailedEi+0xde) [0xacc8ee]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo7LogFile17synchronousAppendEPKvm+0x14f) [0xae4b3f]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur7Journal7journalERKNS0_11JSectHeaderERKNS_14AlignedBuilderE+0x1e5) [0x73b215]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur14WRITETOJOURNALENS0_11JSectHeaderERNS_14AlignedBuilderE+0x32) [0x73b442]
/usr/local/mongodb-current/bin/mongod() [0x73104b]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur11DurableImpl9commitNowEv+0x1a) [0x73157a]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur11DurableImpl16_aCommitIsNeededEv+0x14c) [0x72ef8c]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo3dur11DurableImpl14commitIfNeededEb+0x4c) [0x72f09c]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo13compactExtentEPKcPNS_16NamespaceDetailsENS_7DiskLocEiRKN5boost12scoped_arrayINS_9IndexSpecEEERNS6_INS_12SortPhaseOneEEEibdi+0x516) [0x57cb06]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo8_compactEPKcPNS_16NamespaceDetailsERSsbRNS_14BSONObjBuilderEdi+0x142d) [0x57ecdd]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo7compactERKSsRSsbRNS_14BSONObjBuilderEdi+0x277) [0x57fb47]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo10CompactCmd3runERKSsRNS_7BSONObjEiRSsRNS_14BSONObjBuilderEb+0x950) [0x582cf0]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo12_execCommandEPNS_7CommandERKSsRNS_7BSONObjEiRNS_14BSONObjBuilderEb+0x51) [0x6e8e51]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo11execCommandEPNS_7CommandERNS_6ClientEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb+0xd52) [0x6ea6c2]
/usr/local/mongodb-current/bin/mongod(_ZN5mongo12_runCommandsEPKcRNS_7BSONObjERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi+0x2ac) [0x6eb67c]