[Swift-devel] Clustering and Temp Dirs with Swift

[Andrew Robert Jamieson]

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?

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.

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
>>> _______________________________________________
>>> Swift-devel mailing list
>>> 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/
> ============================================
> ============================================
>
>