问题描述
我们每小时收到大约10000条消息.我们将它们作为单个文件存储在ext3文件系统上的每小时目录中.文件名包含序列号.我们使用rsync每20秒在另一个位置镜像这些文件(通过SAN，但这没关系).
we are receiving about 10000 messages per hour. We store them as individual files in hourly directories on an ext3 filesystem. The file name includes a sequence number. We use rsync to mirror these files every 20 seconds at another location (via a SAN, but that doesn't matter).
有时rsync运行会拾取文件n-3，n-2，n-1，n + 1，然后下一次rsync运行会继续运行n，n + 2，n + 3，n + 4，依此类推.
Sometimes an rsync run picks up files n-3, n-2, n-1, n+1, and then next rsync run continues with n, n+2, n+3, n+4 and so on.
当一个进程在目录中以特定顺序创建文件时，是否有另一个进程使用readdir()看到文件以不同顺序出现?
Is it possible that when one process creates files in a certain sequence within a directory, that another process using readdir() sees the files appearing in a different sequence?
亲切的问候，塞巴斯蒂安
Kind regards,Sebastian
推荐答案
我想您的问题可以重述为:
I suppose your question can be restated as:
答案是肯定的. readdir的排序保证确实非常弱.
The answer is Yes. The ordering guarantees for readdir are very weak indeed.
如果要强制执行排序，则在创建每个文件后，需要为目录d本身显式地fsync()一个文件描述符.
If you want to enforce an ordering, you will need to explicitly fsync() a file descriptor for the directory d itself after creating each file.
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