解决磁盘使用量显示和实际使用量有误差的问题

最近一台机器出现过几次磁盘使用量报警的情况，经过排查，出现下面的问题

df -lh
/dev/sda3              12G   10G  1.1G  91% /usr
使用超过91%了，需要删除一些文件，但是查看磁盘使用情况

du -sm /usr/*|awk '{sum+=$1}END{print sum}'
使用5191M空间，占用不到50%，这是什么情况呢？

经过咨询，是因为之前升级php的时候，虽然将原始的php文件夹（约5G）删除了，但是服务器上还有php进程没有重启，还在占用这个文件夹内的文件，所以导致文件夹删除了，但是实际空间没有释放，系统还是显示占用了10G空间（刚才计算出来的5G+未释放的5G），所以需要重启这个进程，以便让系统真正释放空间。

lsof|grep delete
php         329    root  txt       REG                8,3   21235668              1606441 /usr/local/php-5.2.17/bin/php (deleted)
php         329    root    9r      REG                8,1       1519                32829 /etc/hosts~ (deleted)
jpool_age  1451    root    2u      CHR              136,0                               2 /dev/pts/0 (deleted)
jpool_age  1454    root    2u      CHR              136,0                               2 /dev/pts/0 (deleted)
jpool_age  1454    root    3u      REG                8,7          0             57737233 /data0/trunk/soft/agent/.jpool_agent.lock (deleted)
php        4879    root  txt       REG                8,3   21235668              1606441 /usr/local/php-5.2.17/bin/php (deleted)
sh         5155    root    0u      CHR              136,3                               5 /dev/pts/3 (deleted)
sh         5155    root    1u      CHR              136,3                               5 /dev/pts/3 (deleted)
sh         5155    root    2u      CHR              136,3                               5 /dev/pts/3 (deleted)
php        6145    root  txt       REG                8,3   21278898              1153063 /usr/home/lvbin1/php-lvbin/bin/php (deleted)
sh        10208    root    1w      REG                8,3 5314007509              1344408 /usr/home/xianjun/logs-admin/stats (deleted)
sh        10208    root    2w      REG                8,3 5314007509              1344408 /usr/home/xianjun/logs-admin/stats (deleted)
php       13263    root  txt       REG                8,3   21235668              1606441 /usr/local/php-5.2.17/bin/php (deleted)
php       13964    root  txt       REG                8,3   21278898              1153063 /usr/home/lvbin1/php-lvbin/bin/php (deleted)
sleep     22755    root    1w      REG                8,3 5314007509              1344408 /usr/home/xianjun/logs-admin/stats (deleted)
sleep     22755    root    2w      REG                8,3 5314007509              1344408 /usr/home/xianjun/logs-admin/stats (deleted)
php       23202    root    2u      CHR              136,6                               8 /dev/pts/6 (deleted)
sleep     23303    root    0u      CHR              136,1                               3 /dev/pts/1 (deleted)
sleep     23303    root    1u      CHR              136,1                               3 /dev/pts/1 (deleted)
sleep     23303    root    2u      CHR              136,1                               3 /dev/pts/1 (deleted)
sleep     23448    root    0u      CHR              136,2                               4 /dev/pts/2 (deleted)
sleep     23448    root    1u      CHR              136,2                               4 /dev/pts/2 (deleted)
sleep     23448    root    2u      CHR              136,2                               4 /dev/pts/2 (deleted)
sh        26088    root    0u      CHR              136,1                               3 /dev/pts/1 (deleted)
sh        26088    root    1u      CHR              136,1                               3 /dev/pts/1 (deleted)
sh        26088    root    2u      CHR              136,1                               3 /dev/pts/1 (deleted)

过滤一下/usr目录的内容发现以前删除的目录还在，so...
lsof|grep php-lvbin
php        6145    root  txt       REG                8,3   21278898              1153063 /usr/home/lvbin1/php-lvbin/bin/php (deleted)
php       13964    root  txt       REG                8,3   21278898              1153063 /usr/home/lvbin1/php-lvbin/bin/php (deleted)

查看进程6145和13964还在呢，所以重启这两个任务就可以了。