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List:       ilug
Subject:    Re: [ILUG] USB mass storage woes
From:       Ronan Cunniffe <rcunniff () stp ! dias ! ie>
Date:       2004-07-30 20:10:28
Message-ID: Pine.LNX.4.58.0407302056570.15773 () synge ! stp ! dias ! ie
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On Fri, 30 Jul 2004, ger wrote:

>  From man mount page
> sync    All I/O to the file system  should  be  done synchronously.
>
> To me this means that all I/O operations occur at the same time. This

No.  It means that I/O is done at the time you ask.  Asynchronous means
you ask for the I/O to be done, and then you go away again, and the IO
happens at some later time.

> opposite. I cannot see how this option in mount will prevent or reduce data
> loss from unexpected disconnections during write operations.

It won't reduce the data loss, it reduces the chance of data loss - the
window of opportunity is smaller.

Synchronous is "slower" because a) the writing application is locked up
for the duration and b) every write goes through to the device in this
way, whereas in the asynchronous case, the application might
modify the same part of the file multiple times before the device driver
got to it, in which case it is written only once.

Ronan
-- 
Irish Linux Users' Group
http://www.linux.ie/mailman/listinfo/ilug/

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