为什么 Inode 文件大小与实际大小不同

Question

为什么 Inode 文件大小与实际大小不同

我注意到一个日志文件的大小比 inode 中提到的要小。

$ ls -lhtr /var/log/test/fk-3p-kafka/kafkaServer-gc.log
-rw-r--r-- 1 fk-3p-kafka fk-3p 11G Apr 10 18:27 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
$ du -sh /var/log/test/fk-3p-kafka/kafkaServer-gc.log
2.4G    /var/log/test/fk-3p-kafka/kafkaServer-gc.log
$# stat /var/log/test/fk-3p-kafka/kafkaServer-gc.log
  File: `/var/log/test/fk-3p-kafka/kafkaServer-gc.log'
  Size: 11038186491 Blocks: 4823840    IO Block: 4096   regular file
Device: fe01h/65025d    Inode: 132380      Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 7100/fk-3p-kafka)   Gid: ( 7100/   fk-3p)
Access: 2016-03-09 22:47:06.822168512 +0530
Modify: 2016-04-10 18:28:11.022285512 +0530
Change: 2016-04-10 18:28:11.022285512 +0530
 Birth: -

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接下来我做的是检查任何已删除的文件处理程序。

$ lsof | grep kafkaServer-gc.log
java      22252       fk-3p-kafka    3w      REG              254,1 11038227512     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252   347 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252   712 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252   764 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  2538 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  3241 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  3498 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  4146 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  4147 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  4148 fk-3p-kafka    3w      REG              254,1 11038224580     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  6935 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  7650 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  9530 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252  9581 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 10816 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 11887 fk-3p-kafka    3w      REG              254,1 11038227512     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 13732 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22255 fk-3p-kafka    3w      REG              254,1 11038204079     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22256 fk-3p-kafka    3w      REG              254,1 11038204079     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22257 fk-3p-kafka    3w      REG              254,1 11038204079     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22258 fk-3p-kafka    3w      REG              254,1 11038204079     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22259 fk-3p-kafka    3w      REG              254,1 11038204079     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22260 fk-3p-kafka    3w      REG              254,1 11038204079     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22261 fk-3p-kafka    3w      REG              254,1 11038205544     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22262 fk-3p-kafka    3w      REG              254,1 11038205544     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22263 fk-3p-kafka    3w      REG              254,1 11038205544     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22264 fk-3p-kafka    3w      REG              254,1 11038205544     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22265 fk-3p-kafka    3w      REG              254,1 11038205544     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22266 fk-3p-kafka    3w      REG              254,1 11038205544     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22267 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22268 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22269 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22270 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22271 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22272 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22273 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22274 fk-3p-kafka    3w      REG              254,1 11038207009     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22275 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22276 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22277 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22278 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22279 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22280 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22281 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22282 fk-3p-kafka    3w      REG              254,1 11038208473     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22283 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22284 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22285 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22286 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22287 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22288 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22289 fk-3p-kafka    3w      REG              254,1 11038209937     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22290 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22291 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22292 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22293 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22294 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22295 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22296 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22297 fk-3p-kafka    3w      REG              254,1 11038211401     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22298 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22299 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22300 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22301 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22302 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22303 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22304 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22305 fk-3p-kafka    3w      REG              254,1 11038212865     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22306 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22307 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22308 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22309 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22310 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22311 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22312 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22313 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22317 fk-3p-kafka    3w      REG              254,1 11038214329     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22318 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22319 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22320 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22321 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22322 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22323 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22324 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22325 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22326 fk-3p-kafka    3w      REG              254,1 11038215793     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22327 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22328 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22329 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22330 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22331 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22332 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22333 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22334 fk-3p-kafka    3w      REG              254,1 11038217258     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22335 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22336 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22337 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22338 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22339 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22340 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22341 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22342 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22343 fk-3p-kafka    3w      REG              254,1 11038218724     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22344 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22345 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22349 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22352 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22367 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 22450 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26510 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26511 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26740 fk-3p-kafka    3w      REG              254,1 11038220188     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26741 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26749 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26750 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26758 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 26759 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 28172 fk-3p-kafka    3w      REG              254,1 11038227512     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 28173 fk-3p-kafka    3w      REG              254,1 11038227512     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 28174 fk-3p-kafka    3w      REG              254,1 11038227512     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 31036 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 31187 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 31339 fk-3p-kafka    3w      REG              254,1 11038221652     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 31389 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 31692 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32151 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32350 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32452 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32603 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32606 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32607 fk-3p-kafka    3w      REG              254,1 11038226047     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32608 fk-3p-kafka    3w      REG              254,1 11038227512     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32654 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log
java      22252 32755 fk-3p-kafka    3w      REG              254,1 11038223116     132380 /var/log/test/fk-3p-kafka/kafkaServer-gc.log

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很明显，kafkaServer-gc.log 没有删除的 FD。我也尝试截断文件，但 inode 中的文件大小没有改变。这种行为的原因是什么？

Answer 1

Gil*_*il' 8

鉴于这是一个日志文件，以下是最可能的解释：

有一个进程打开了文件并不断附加到它。当前是进程 22252，过去可能有其他进程（同一应用程序的先前实例）。
在过去的某个时候，有人截断了文件。将文件截断到某个位置会删除该位置之后的所有数据，但不会影响附加到文件的进程的位置。

假设文件被截断到位置 0。然后，在截断操作之后，文件大小立即为 0。但是 Java 进程打开了文件，并将其当前位置设置为n。下一次 Java 进程写入日志文件时，它从位置n写入到n + k（其中k是它写入的字节数），因此在此之后文件大小为n + k，并且继续增长随着Java进程写得更多。

磁盘使用量¹小于文件大小，因为截断删除了用于文件内容的所有存储空间。当进程在截断后附加到文件时，将文件变成稀疏文件：位置n之前的所有字节都是空字节，但不会重新创建完全由空字节组成的块。假设n = 1024567 且块大小为 1024 字节，然后在截断后的第一次追加操作中，创建了位置为 1024000–1025023 的块，其中有 567 个空字节，后跟该日志消息的k字节。

删除仍处于打开状态的文件不会影响其磁盘使用情况或文件大小，但会使该文件不可见du，ls同时仍会占用记录为正在使用的空间df。请参阅为什么有这么多不同的方法来衡量磁盘使用情况？

¹_{文件使用的块数——它和文件大小都存储在 inode 中，所以不要将磁盘使用情况称为“inode 文件大小”！}

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