[Swift-devel] Clustering and Temp Dirs with Swift
Ioan Raicu
iraicu at cs.uchicago.edu
Fri Oct 26 16:23:12 CDT 2007
Hi,
Andrew Robert Jamieson wrote:
> Ioan,
>
> Thanks for the explaination. It seems like you characterized what
> is going on pretty well.
>
> One question I have is, does this case occur only for situations in
> which it is in the same directory or is it anywhere at any given time
> in the shared GPFS?
>
I don't know, but as far as I can tell, Swift will create these temp
scratch directories per job in the same subdirectory (Mihael or Ben,
please correct me if I am wrong on this). I have seen this behavior for
certain in this case, but am not sure if things get better if you were
to work in completely separate parts of the filesystem.
> Furthermore, why can't the short lived directory live on the local
> node's /tmp/* somewhere? I have wrapped all my programs to ensure
> that things are ONLY executed on the local node directories to
> specifically aviod this type of problem. Now Swift is making that
> effort irrelevant it seems.
They could, with some modifications to the wrapper script. Or with some
higher level logic that manages the data on the local disk and moves it
in and out from and to the shared file system. Your short term
solution would probably be the first option, changing the wrapper script
to support local disk usage. Maybe there are other solutions as well.
Ioan
>
> Does this seem reasonable?
>
> Thanks,
> Andrew
>
> On Fri, 26 Oct 2007, Ioan Raicu wrote:
>
>> I am not sure what configuration exists on TP, but on the TeraGrid
>> ANL/UC cluster, with 8 servers behind GPFS, the wrapper script
>> performance (create dir, create symbolic links, remove directory...
>> all on GPFS) is anywhere between 20~40 / sec, depending on how many
>> nodes you have doing this concurrently. The throughput increases
>> first as you add nodes, but then decreases down to about 20/sec with
>> 20~30+ nodes. What this means is that even if you bundle jobs up,
>> you will not get anything better than this, throughput wise,
>> regardless of how short the jobs are. Now, if TP has less than 8
>> servers, its likely that the throughput it can sustain is even lower,
>> and if you push it over the edge, even to the point of thrashing
>> where the throughput can be extremely small. I don't have any
>> suggestions of how you can get around this, with the exception of
>> making your job sizes larger on average, and hence have fewer jobs
>> over the same period of time.
>>
>> Ioan
>>
>> Andrew Robert Jamieson wrote:
>>> I am kind of at a stand still for getting anything done on TP right
>>> now with this problem. Are there any suggestions to overcome this
>>> for the time being?
>>>
>>> On Fri, 26 Oct 2007, Andrew Robert Jamieson wrote:
>>>
>>>> Hello all,
>>>>
>>>> I am encountering the following problem on Teraport. I submit a
>>>> clustered swift WF which should amount to something on the order of
>>>> 850x3 individual jobs total. I have clustered the jobs because they
>>>> are very fast (somewhere around 20 sec to 1 min long). When I
>>>> submit the WF on TP things start out fantastic, I get 10s of output
>>>> files in a matter of seconds and nodes would start and finish
>>>> clustered batches in a matter of minutes or less. However, after
>>>> waiting about 3-5 mins, when clustered jobs are begin to line up in
>>>> the queue and more start running at the same time, things start to
>>>> slow down to a trickle in terms of output.
>>>>
>>>> One thing I noticed is when I try a simply ls on TP in the swift
>>>> temp running directory where the temp job dirs are created and
>>>> destroyed, it take a very long time. And when it is done only five
>>>> or so things are in the dir. (this is the dir with "info
>>>> kickstart shared status wrapper.log" in it). What I think is
>>>> happening is that TP's filesystem cant handle this extremely rapid
>>>> creation/destruction of directories in that shared location. From
>>>> what I have been told these temp dirs come and go as long as the
>>>> job runs successfully.
>>>>
>>>> What I am wondering is if there is anyway to move that dir to the
>>>> local node tmp diretory not the shared file system, while it is
>>>> running and if something fails then have it sent to the appropriate
>>>> place.
>>>>
>>>> Or, if another layer of temp dir wrapping could be applied with
>>>> labeld perhaps with respect to the clustered job grouping and not
>>>> simply the individual jobs (since there are thousands being
>>>> computed at once).
>>>> That these things would only be generated/deleted every 5 mins or
>>>> 10 mins (if clustered properly on my part) instead of one event
>>>> every milli second or what have you.
>>>>
>>>> I don't know which solution is feasible or if any are at all, but
>>>> this seems to be a major problem for my WFs. In general it is
>>>> never good to have a million things coming and going on a shared
>>>> file system in one place, from my experience at least.
>>>>
>>>>
>>>> Thanks,
>>>> Andrew
>>>> _______________________________________________
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>>>> Swift-devel at ci.uchicago.edu
>>>> http://mail.ci.uchicago.edu/mailman/listinfo/swift-devel
>>>>
>>> _______________________________________________
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>>
>> --
>> ============================================
>> Ioan Raicu
>> Ph.D. Student
>> ============================================
>> Distributed Systems Laboratory
>> Computer Science Department
>> University of Chicago
>> 1100 E. 58th Street, Ryerson Hall
>> Chicago, IL 60637
>> ============================================
>> Email: iraicu at cs.uchicago.edu
>> Web: http://www.cs.uchicago.edu/~iraicu
>> http://dsl.cs.uchicago.edu/
>> ============================================
>> ============================================
>>
>>
>
--
============================================
Ioan Raicu
Ph.D. Student
============================================
Distributed Systems Laboratory
Computer Science Department
University of Chicago
1100 E. 58th Street, Ryerson Hall
Chicago, IL 60637
============================================
Email: iraicu at cs.uchicago.edu
Web: http://www.cs.uchicago.edu/~iraicu
http://dsl.cs.uchicago.edu/
============================================
============================================
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