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Re: Sync file on write?

Subject: Re: Sync file on write?
From: Paul Hartman
Date: Sun, 27 Dec 2009 16:35:21 -0600
On Sun, Dec 27, 2009 at 4:30 PM, Theodore Kilgore
<[email protected]> wrote:
>
>
> On Sun, 27 Dec 2009, Paul Hartman wrote:
>
>> Hi,
>>
>> I have a USB device and write speed is terrible when I copy more than
>> 1 file to it (it is mounted in async mode). If I copy just one file
>> and sync, speed is 17MB/sec, if I copy more than 1 file the speed
>> drops well below 2MB/sec. This does not happen on MS Windows so I
>> think it's some side-effect of linux i/o flushing creating multiple
>> write-streams or something like this.
>>
>> Anyway, I'm trying to work-around this and wonder if there is a way I
>> can tell MC to sync/fsync (whatever means ensure file is written to
>> disk physically) after each file? If it would apply only to writes
>> into this device that would be even better :)
>>
>> thanks
>> paul
>
> Paul,
>
> I have no idea of the cause of this. I am not a specialist in Midnight
> Commander to any extent whatsoever. I do know a bit more about USB, but I
> have never delved very much into questions of speed.
>
> Keeping the above disclaimers in mind, it does appear to me that there is a
> simple test which might help to localize the problem.
>
> Can you set up a situation in which the slowdown occurs in Midnight
> Commander, but it is possible to move the same files from the same source
> location to the same destination using command-line tools only? And run a
> time comparison under both circumstances?
>
> Theodore Kilgore

Hi,

Sorry if I wasn't clear, the problem isn't caused by MC and I don't
think MC has anything to do with it, but it is simply my tool of
choice for everyday working. It happens if I use "cp" from
command-line or copy files from within MC or using GUI tools. In other
words,

this is slow:
cp file1 file2 file3 /mnt/usb; sync

this is fast:
cp file1 /mnt/usb; sync
cp file2 /mnt/usb; sync
cp file3 /mnt/usb; sync

So that's why I was curious if there's any kind of  "after file"
command or option to make it sync to disk after every file.

Thanks,
Paul
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