Re: Appending to an open file - O_APPEND flag

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Hi guy's,

   I am totally new to Ceph deploy and I have succefully install ceph cluster on a Admin node and able to active it by One monitor and two OSD. After creation of Ceph Cluster I checked the Ceph Health Status and The output was OK.
  With that success I started to move to next stage for Rados Gateway. Untill 90% of work there was no any error but when I moved with stage python s3test.py I am facing the error. 
  It's kind request to share your views to solve the error.

thanks n advance,
Maddy

On Tue, Sep 1, 2015 at 5:40 PM, Janusz Borkowski <janusz.borkowski@xxxxxxxxxxxxxx> wrote:
Hi!

open( ... O_APPEND) works fine in a single system. If many processes write to the same file, their output will never overwrite each other.

On NFS overwriting is possible, as appending is only emulated - each write is preceded by a seek to the current file size and race condition may occur.

How it is in cephfs?

I have a file F opened with  O_APPEND|O_WRONLY by some process. In a console I type

    $ echo "asd" >> F

Effectively, this is opening of file F by another process with O_APPEND flag .

The string "asd" is written to the beginning of file F, overwriting the starting bytes in the file. Is it a bug or a feature? If a feature, how it is described?

It is ceph Hammer and kernel 3.10.0-229.11.1.el7.x86_64

Thanks!

J.

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