[Go-essp-tech] Bulk data moving: the UNIDATA LDM and other options

Mon Jun 14 00:45:50 MDT 2010

Hello Rachana, David,

Thanks for those comments. If passed the UDT paper onto Dave Terrett who is the technical expert on our network issues. The offer of help with globus.org is very attractive -- I'll have a look back at our data moving plans and see if we can come up with some requirements.

He is in touch with ESnet -- using their machines as US hosts to test our transfer rates. I'll check with him see who is in touch with and whether we can get some higher level support from them. 

cheers,
Martin  

-----Original Message-----
From: Rachana Ananthakrishnan [mailto:ranantha at mcs.anl.gov]
Sent: Fri 11/06/2010 22:35
To: Juckes, Martin (STFC,RAL,SSTD)
Cc: don at ucar.edu; go-essp-tech at ucar.edu
Subject: Re: [Go-essp-tech] Bulk data moving and the UNIDATA LDM

Hi Martin,

At this point the globus.org work is pre-production, although it  
builds on our stable data transfer software, GridFTP.  We are actively  
engaging with user communities, and working with them to use this  
solution for their data transfer needs. We have seen success in the  
specific functionality required by the communities we have engaged  
with, and are in the process of prioritizing feature additions based  
on feedback we are getting. It would be good for us to evaluate  
globus.org to see if it fits as a solution for our use case. If there  
is interest, I am happy to take back requirements from this group to  
evaluate the globus.org solution in terms of features offered, and  
planned roadmap. It will help us determine if we can leverage it, and  
how and when we could engage.

Regarding the intercontinental transfers, I took the question back to  
our data transfer folks, and here is their response. Attached is also  
a reference paper from them on studies with using UDT with GridFTP for  
such transfers:

"We have seen data rates around only 50 mbps or less using TCP between  
US and both Australia and New Zealand. We haven't done any detailed  
analysis of the packet loss rates but this is probably due to the  
inherent limitations in TCP on high-latency links. The latency to  
australia and NZ is more than 200 ms. Using UDT as an alternative to  
TCP has helped improve the performance by 4x. Enclosed paper has some  
data comparing GridFTP over TCP and GridFTP over UDT for transfers  
between US and NZ.
Note that these are straight globus-url-copy transfers and not  
Globus.org transfers."

Also, in the original link I sent, you pointed out the retries  
mentioned in the study. Those retries were actually for transfers with  
in Australia, and not intercontinental transfer. Run 5 and Run 6 in  
the link http://www.mcs.anl.gov/~childers/VPAC/, were for sites within  
Australia.

Hope this helps,
Rachana

On Jun 10, 2010, at 2:50 AM, <martin.juckes at stfc.ac.uk> <martin.juckes at stfc.ac.uk 
 > wrote:

> Hello Rachana,
>
> Thanks for those useful examples. My main interest with LDM was the  
> fire-and-forget feature, which simplifies management of a data- 
> stream.  The phrase I used, "verify success", was not really  
> accurate -- what I should of said was guarantee success.
>
> It sounds as though I also got a mis-leading view of the maturity of  
> globus.org from the web sites I found on the topic -- my apologies  
> for that.
>
> On a slightly different topic, a quick look at the links you sent  
> appears to reflect similar problems with long range transfers to  
> ones we are encountering. We have also been doing trials with  
> GridFTP looking at transfer rates between here (southern England)  
> and France, Germany and the US. Transfer rates to the US are  
> substantially slower, reflecting high package loss rates. It looks  
> as though there is an important distinction to be made between wide  
> area networks within Europe or within the US, for which very high  
> transfer rates can be achieved, and global networks, for which  
> package loss appears to seriously throttle transfer rates. This  
> problem is reflected in the first link you sent, with high resend  
> rates to Australia compared with very small number on trials with  
> larger files in the US.
>
> This is an important issue for us because we need to move a lot of  
> data around the world and the current transfer rates we are getting  
> are not likely to be sufficient. Do you know of any work on  
> assessing and alleviating package loss on intercontinental  
> transfers? (I'm not expecting LDM to provide any improvement in this  
> area -- but it would be a very welcome surprise if it did).
>
> regards,
> Martin
>
> -----Original Message-----
> From: Rachana Ananthakrishnan [mailto:ranantha at mcs.anl.gov]
> Sent: Thu 10/06/2010 03:46
> To: Juckes, Martin (STFC,RAL,SSTD)
> Cc: don at ucar.edu; go-essp-tech at ucar.edu
> Subject: Re: [Go-essp-tech] Bulk data moving and the UNIDATA LDM
>
> Hi,
>
> I wanted to address some points raised on this thread, and also
> provide pointers to some relevant material.
>
> On the GridFTP transfer with small files, there has been significant
> work to improve performance with small files. Here is a reference that
> explains this work: http://www.mcs.anl.gov/~kettimut/publications/Pipelining.pdf
> . Is the concern of using GridFTP for small files a performance issue
> or a reliability issue?
>
> It is hard to compare performance without hard numbers, but taking
> this thread back to our GridFTP team, here are some questions that
> were raised:
>
>  - Checksums at end of transfer is supported by the GridFTP client
> libraries. What additional features are covered by the statement "LDM
> appears to have a lot of good features built in to verify success of
> data transfer between sites".
> - GridFTP supports both concurrent transfer of multiple files and
> concurrent transfer of multiple chunks within a file. This combination
> can outperform just concurrent transfer of multiple files on high
> latency links. Is there comparable feature with LDM?
> - What security model does LDM support?
>
> Regarding globus.org, it is built around GridFTP server and client
> technology to provide the fire and forget mode for file transfers.
> Like Pauline mentions, it at the minimum, provides reliability, and
> restarts with the transfers. It is provided as a Software as a Service
> solution around GridFTP software that is both mature and robust, and
> will be provided as a hosted solution operated by us (Argonne National
> Lab in the US) for user communities. We are working with individual
> communities to do performance and reliability testing, and to gather
> specific requirements from them. Integrity check is one of the
> features in the pipeline. Some references to performance numbers thus
> far:
>
> Transfer managed from a site in US to Australia: http://www.mcs.anl.gov/~childers/VPAC/
> Transfer test for tutorials: http://www.mcs.anl.gov/~childers/GlobusWorld2010/results.html
>
> Alex referenced a Super Computing Bandwidth Challenge work that used
> globus.org to replicate 10TB of CMIP3 data between two sites in the
> US: http://www.mcs.anl.gov/~kettimut/publications/ 
> HPDC10_BWC_Final.pdf.
>
> If there is of interest in this group, like Pauline suggested, we
> could have someone from our team present about the service to this
> group. We are certainly interested to hear experiences with LDM, and
> experiences on using both these solutions.
>
> Thanks,
> Rachana
>
>
> On Jun 7, 2010, at 12:04 PM, <martin.juckes at stfc.ac.uk> <martin.juckes at stfc.ac.uk
>> wrote:
>
>> Hello Don, Pauline,
>>
>> I had a quick look at globus.org -- it looks good but is only
>> available
>> as a beta release, whereas LDM is on version 6.8. Having a tried and
>> tested bit of software to handle a key part of our data management
>> would
>> make life a lot easier.
>>
>> Form Don's message, it appears that LDM does not have GridFTP's
>> ability
>> to deal with large files. So, we have a choice between LDM which
>> supports a "fire-and-forget" approach but needs small files or
>> GridFTP,
>> which will deal with small files but requires additional software to
>> determine whether transfer succeeded.
>>
>> It looks to me as though LDM has a big advantage in terms of
>> maturity. I
>> think the overhead of having to split and rejoin files is likely to  
>> be
>> significantly less problematic than getting reliable site to site
>> communication about thousands of files being transferred.
>>
>> Cheers,
>> Martin
>>
>>> -----Original Message-----
>>> From: Don Middleton [mailto:don at ucar.edu]
>>> Sent: 07 June 2010 13:11
>>> To: Juckes, Martin (STFC,RAL,SSTD)
>>> Cc: Don Middleton; Lawrence, Bryan (STFC,RAL,SSTD); go-essp-
>>> tech at ucar.edu
>>> Subject: Re: [Go-essp-tech] Bulk data moving and the UNIDATA LDM
>>>
>>> I don't have figures, but some general information. In the TIGGE
>>> context, LDM is dealing with pretty small packages: 2D grids, which
>>> can be reassembled at the receiving end into individual 3D fields  
>>> for
>>> each timestep and forecast. Cost of transmission failure for large
>>> files is reported to be high, but LDM does have features to support
>>> retry until success. I don't know how difficult it might be to
>>> replace
>>> LDM's transport layer with GridFTP, or even if it makes any sense to
>>> think about that, particularly given Pauline's message. LDM does
>>> appear to be working quite well in an operational context.
>>>
>>> don
>>>
>>>
>>> On Jun 7, 2010, at 1:50 AM, <martin.juckes at stfc.ac.uk>
>>> <martin.juckes at stfc.ac.uk
>>>> wrote:
>>>
>>>> Thanks Don, that would be interesting to see. The TIGGE data
>>> transfers
>>>> are the same scale as we will have to deal with, nso the figures
>>>> will be
>>>> very relevant.
>>>>
>>>> I was interested in LDM because it appears to offer a lot of  
>>>> support
>>>> for
>>>> data management which might significantly reduce the amount of
>> coding
>>>> and design we need to do ourselves -- relative to what would be
>>>> necessary with GridFTP.
>>>>
>>>> Regards,
>>>> Martin
>>>>
>>>>> -----Original Message-----
>>>>> From: go-essp-tech-bounces at ucar.edu [mailto:go-essp-tech-
>>>>> bounces at ucar.edu] On Behalf Of Don Middleton
>>>>> Sent: 04 June 2010 16:29
>>>>> To: Lawrence, Bryan (STFC,RAL,SSTD)
>>>>> Cc: go-essp-tech at ucar.edu
>>>>> Subject: Re: [Go-essp-tech] Bulk data moving and the UNIDATA LDM
>>>>>
>>>>> We're using LDM for TIGGE, and replicating a couple of terabytes  
>>>>> of
>>>>> forecast data a week, around the world. I'll inquire about
>> filesizes
>>>>> and rates.
>>>>>
>>>>> don
>>>>>
>>>>>
>>>>> On Jun 4, 2010, at 9:15 AM, Bryan Lawrence wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> My understanding is that it doesn't compare on a file by file
>>> basis:
>>>>>> GridFTP is clearly optomised to move big files fast. However, if
>> we
>>>>>> are
>>>>>> moving more than dozens of files (as we are), then as I  
>>>>>> understand
>>>>> it,
>>>>>> LDM would open multiple file transfer streams, so GridFTP's
>>>> advantage
>>>>>> will boil down to the (not inconsiderable) negotiated window  
>>>>>> size.
>>>>>>
>>>>>> Someone else ought to be able to give much better information  
>>>>>> than
>>>>>> that
>>>>>> :-)
>>>>>>
>>>>>> Cheers
>>>>>> Bryan
>>>>>>
>>>>>>
>>>>>> On Friday 04 Jun 2010 15:58:33 Alex Sim wrote:
>>>>>>> Can you tell us  about the wide-area transfer performance with
>>>>>>> Unidata LDM compared to GridFTP server based transfers?
>>>>>>>
>>>>>>>
>>>>>>> -- Alex
>>>>>>>
>>>>>>> On 6/4/10 3:39 AM, martin.juckes at stfc.ac.uk wrote:
>>>>>>>
>>>>>>> Hello all,
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> There may be a simple answer to this, but is there a reason why
>> we
>>>>>>> shouldn't use the Unidata Local Data Manager (LDM) for bulk data
>>>>>>> movement within the CMIP5 distributed archive? It appears to  
>>>>>>> have
>>> a
>>>>>>> lot of good features built in to verify success of data transfer
>>>>>>> between sites, and runs successfully at many operational sites.
>>>> This
>>>>>>> would simplify the work flow, since all the complexity of the
>> site
>>>>>>> to site transfers would be dealt with by a tried and tested
>>> system,
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> Martin
>>>>>>>
>>>>>>
>>>>>> --
>>>>>> Bryan Lawrence
>>>>>> Director of Environmental Archival and Associated Research
>>>>>> (NCAS/British Atmospheric Data Centre and NCEO/NERC NEODC)
>>>>>> STFC, Rutherford Appleton Laboratory
>>>>>> Phone +44 1235 445012; Fax ... 5848;
>>>>>> Web: home.badc.rl.ac.uk/lawrence
>>>>>> _______________________________________________
>>>>>> GO-ESSP-TECH mailing list
>>>>>> GO-ESSP-TECH at ucar.edu
>>>>>> http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
>>>>>
>>>>> _______________________________________________
>>>>> GO-ESSP-TECH mailing list
>>>>> GO-ESSP-TECH at ucar.edu
>>>>> http://mailman.ucar.edu/mailman/listinfo/go-essp-tech
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>
> Rachana Ananthakrishnan
> Argonne National Lab | University of Chicago
>
>
>
>
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Rachana Ananthakrishnan
Argonne National Lab | University of Chicago

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