[Swift-devel] Re: swift-falkon problem

[Ioan Raicu]

Here is more on sync:
> According to the standard specification (e.g., POSIX.1-2001), sync() 
> schedules the writes, but  may  return  before  the
>        actual  writing  is  done.  However, since version 1.3.20 Linux 
> does actually wait.  (This still does not guarantee data
>        integrity: modern disks have large caches.)
So, it looks like it might be blocking, but it might depend on the Linux 
kernel.  Anyways, I think its worth a try, and it seems like a better 
solution than sleeps.

Ioan

Ioan Raicu wrote:
> I added a configurable delay in delivering notifications to Swift in 
> the provider code, which Mike still has to test.  The deef provider 
> already had a queue for the incoming notifications, so it was not hard 
> to delay these notifications from this queue to Swift.
>
> Another approach, which I discussed with Mike, was to do a sync at the 
> end of the wrapper script.  From my simple test on a linux box, it 
> seems that sync is a blocking call, which is exactly what we want!
> iraicu at gto:~> time sync
> real    0m0.711s
> user    0m0.000s
> sys     0m0.004s
> iraicu at gto:~> time sync
> real    0m0.035s
> user    0m0.000s
> sys     0m0.000s
>
> Mike, could you try adding a sync at the end of the wrapper.sh (and 
> make sure to not have any additional sleeps anywhere else), and see if 
> that helps?
>
> Ioan
>
>
> Ben Clifford wrote:
>> There is flag for NFS mounts, 'noac', which disables attribute 
>> caching on clients, which I think may make the fielsystem behave in 
>> the desired fashion; however it sounds like it also massively reduces 
>> filesystem performance and fileserver load.
>>
>> Mike, you might be able to persuade MCS systems to make such a 
>> filesystem available.
>>
>> I suspect some multi-second delay after touching the status file and 
>> before exiting in the wrapper script is probably the best workaround 
>> for now, though.
>>
>>   
>

-- 
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Ioan Raicu
Ph.D. Candidate
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Distributed Systems Laboratory
Computer Science Department
University of Chicago
1100 E. 58th Street, Ryerson Hall
Chicago, IL 60637
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Email: iraicu at cs.uchicago.edu
Web:   http://www.cs.uchicago.edu/~iraicu
http://dev.globus.org/wiki/Incubator/Falkon
http://dsl-wiki.cs.uchicago.edu/index.php/Main_Page
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