The document discusses the challenges and solutions for data movement between distributed repositories in large-scale collaborative science, focusing on the Petashare environment in Louisiana, which utilizes advanced middleware and tools for efficient data management. Key components include data transfer protocols like Stork for scheduling, adaptive tuning for performance optimization, and failure awareness to enhance reliability during data transfers. It also covers future directions for improving these systems through dynamic scheduling and job aggregation.

1. Data Movement between
Distributed Repositories for
Large Scale Collaborative
Science
Mehmet Balman
Louisiana State University
Baton Rouge, LA

2. Motivation
 Scientific applicationsare becoming more data intensive
(dealing with petabytes of data)
 We use geographically distributed resources to satisfy
immense computational requirements
 The distributed nature of the resources made data
movement is a major bottleneck for end-to-end
application performance
Therefore, complex middleware is required to
orchestrate the use of these storage and network
resources between collaborating parties, and to manage
the end-to-end distribution of data.

3. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

4. PetaShare
• Distributed Storage System in Louisiana
• Spans among seven research institutions
• 300TB of disk storage
• 400TB of tape (will be online soon)
using:
IRODS (Integrated Rule-Oriented Data System)
www.irods.org
PetaShare

5. PetaShare as an example
 Global Namespace among distributed resources
 Client tools and interfaces:
 Pcommands
 Petashell (parrot)
 Petafs (fuse)
 Windows Browser
 Web Portal
General scenario is to use an intermediate storage
area (limited capacity) and then transfer files to a
remote storage for post processing and long term
archival

6. PetaShare Architecture
Fast and Efficient Data Migration in PetaShare ?
LONI (Louisiana Optical Network Initiative)
www.loni.org

7. Lightweight client tools for transparent access
 Petashell, based on Parrot
 Petafs, a FUSE client
In order to improve throughput performance, we've
implemented Advance Buffer Cache in Petafs and
Petashell clients by aggregating I/O requests to minimize
the number of network messages.
Is it efficient for bulk data transfer
PetaShare Client Tools

8. Client performance with Advance Buffer

9. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

10.  Advance Data Transfer Protocols (i.e. GridFTP)
 High throughput data transfer
 Data Scheduler: Stork
 Organizing data movement activities
 Ordering data transfer requests
Moving Large Data Sets

11.  Stork: A batch scheduler for Data Placement
activities
 Supports plug-in data transfer modules for
specific protocols/services
 Throttling: deciding number of concurrent
transfers
 Keep a log of data placement activities
 Add fault tolerance to data transfers
 Tuning protocol transfer parameters (number
of parallel TCP streams)
Scheduling Data Movement Jobs

12. [ dest_url = "gsiftp://eric1.loni.org/scratch/user/";
arguments = -p 4 dbg -vb";
src_url = "file:///home/user/test/";
dap_type = "transfer";
verify_checksum = true;
verify_filesize = true;
set_permission = "755" ;
recursive_copy = true;
network_check = true;
checkpoint_transfer = true;
output = "user.out";
err = "user.err";
log = "userjob.log";
]
Stork Job submission

13. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

14. End-to-end bulk data transfer (latency wall)
 TCP based solutions
 Fast TCP, Scalable TCP etc
 UDP based solutions
 RBUDP, UDT etc
 Most of these solutions require kernel level
changes
 Not preferred by most domain scientists
Fast Data Transfer

15.  Take an application-level transfer protocol (i.e.
GridFTP) and tune-up for better performance:
 Using Multiple (Parallel) streams
 Tuning Buffer size
(efficient utilization of available network capacity)
Level of Parallelism in End-to-end Data Transfer
 number of parallel data streams connected to a data transfer
service for increasing the utilization of network bandwidth
 number of concurrent data transfer operations that are
initiated at the same time for better utilization of system
resources.
Application Level Tuning

16.  Instead of a single connection at a time, multiple
TCP streams are opened to a single data transfer
service in the destination host.
 We gain larger bandwidth in TCP especially in a
network with less packet loss rate; parallel
connections better utilize the TCP buffer available to
the data transfer, such that N connections might be N
times faster than a single connection
 Multiple TCP streams result in extra in the system
Parallel TCP Streams

17. Average Throughput using parallel streams over 1Gbps
Experiments in LONI (www.loni.org) environment - transfer file to
QB from Linux m/c

18. Average Throughput using parallel streams over 1Gpbs
Experiments in LONI (www.loni.org) environment - transfer file to QB from
IBM m/c

19. Average Throughput using parallel streams over 10Gpbs

20. Average Throughput using parallel streams over 10Gpbs

21. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

22.  Can we predict this
behavior?
 Yes, we can come up with
a good estimation for the
parallelism level
 Network statistics
 Extra measurement
 Historical data
Parameter Estimation

23. single stream, theoretical calculation of
throughput based on MSS, RTT and packet
loss rate:
n streams gains as much as total throughput
of n single stream: (not correct)
A better model: a relation is established
between RTT, p and the number of streams n:
Parallel Stream Optimization

24. Parameter Estimation Service

25.  Might not reflect the best possible current settings
(Dynamic Environment)
 What if network condition changes?
 Requires three sample transfers (curve fitting)
 need to probe the system and make
measurements with external profilers
 Does require a complex model for parameter
optimization
Parameter Estimation

26. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

27.  Instead of predictive sampling, use data from
actual transfer
 transfer data by chunks (partial transfers) and
also set control parameters on the fly.
 measure throughput for every transferred data
chunk
 gradually increase the number of parallel
streams till it comes to an equilibrium point
Adaptive Tuning

28.  No need to probe the system and make
measurements with external profilers
 Does not require any complex model for
parameter optimization
 Adapts to changing environment
 But, overhead in changing parallelism level
 Fast start (exponentially increase the number
of parallel streams)
Adaptive Tuning

29.  Start with single stream (n=1)
 Measure instant throughput for every data chunk transferred
(fast start)
 Increase the number of parallel streams (n=n*2),
 transfer the data chunk
 measure instant throughput
 If current throughput value is better than previous one,
continue
 Otherwise, set n to the old value and gradually increase
parallelism level (n=n+1)
 If no throughput gain by increasing number of streams
(found the equilibrium point)
 Increase chunk size (delay measurement period)
Adaptive Tuning

30. Adaptive Tuning: number of parallel streams
Experiments in LONI (www.loni.org) environment - transfer file
to QB from IBM m/c

31. Adaptive Tuning: number of parallel streams
Experiments in LONI (www.loni.org) environment - transfer file to
QB from Linux m/c

32. Adaptive Tuning: number of parallel streams
Experiments in LONI (www.loni.org) environment - transfer file to
QB from Linux m/c

33. Dynamic Tuning Algorithm

34. Dynamic Tuning Algorithm

35. Dynamic Tuning Algorithm

36. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

37. • Dynamic Environment:
• data transfers are prune to frequent failures
• what went wrong during data transfer?
• No access to the remote resources
• Messages get lost due to system malfunction
• Instead of waiting failure to happen
• Detect possible failures and malfunctioning services
• Search for another data server
• Alternate data transfer service
• Classify erroneous cases to make better decisions
Failure Awareness

38. • Use Network Exploration Techniques
– Check availability of the remote service
– Resolve host and determine connectivity failures
– Detect available data transfers service
– should be Fast and Efficient not to bother system/network
resources
• Error while transfer is in progress?
– Error_TRANSFER
• Retry or not?
• When to re-initiate the transfer
• Use alternate options?
Error Detection

39. • Data Transfer Protocol not always return appropriate error codes
• Using error messages generated by the data transfer protocol
• A better logging facility and classification
•Recover from Failure
•Retry failed operation
•Postpone scheduling of
a failed operations
•Early Error Detection
•Initiate Transfer when
erroneous condition
recovered
•Or use Alternate
options
Error Classification

40. Error Reporting

41. Scoop data - Hurricane Gustov Simulations
Hundreds of files (250 data transfer operation)
Small (100MB) and large files (1G, 2G)
Failure Aware Scheduling

42. • Verify the successful completion of the operation
by controlling checksum and file size.
• for GridFTP, Stork transfer module can recover
from a failed operation by restarting from the last
transmitted file. In case of a retry from a failure,
scheduler informs the transfer module to recover
and restart the transfer using the information from
a rescue file created by the checkpoint-enabled
transfer module.
• An “intelligent” (dynamic tuning) alternative to
Globus RFT (Reliable File Transfer)
New Transfer Modules

43. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

44. • Multiple data movement jobs are combined and
processed as a single transfer job
• Information about the aggregated job is stored in the
job queue and it is tied to a main job which is actually
performing the transfer operation such that it can be
queried and reported separately.
• Hence, aggregation is transparent to the user
• We have seen vast performance improvement,
especially with small data files
– decreasing the amount of protocol usage
– reducing the number of independent network
connections
Job Aggregation

45. Experiments on LONI (Louisiana Optical Network Initiative) :
1024 transfer jobs from Ducky to Queenbee (rtt avg 5.129 ms) - 5MB
data file per job
Job Aggregation

46. ➢PetaShare Environment – as an example
➢ Distributed Data Management in Louisiana
➢Data Movement using Stork
➢ Data Scheduling
➢Tuning Data Transfer Operations
➢ Prediction Service
➢ Adaptive Tuning
➢Failure-Awareness
➢Job Aggregation
➢Future Directions
Agenda

47. • Performance bottleneck
– Hundreds of jobs submitted to a single batch
scheduler, Stork
• Single point of failure
Stork: Central Scheduling Framework
Stork

48. • Interaction between data schedulers
– Manage data activities with lightweight agents in
each site
– Job Delegation
– peer-to-peer data movement
– data and server striping
– make use of replicas for multi-source downloads
Distributed Data Scheduling
Future Plans

49. www.petashare.org
www.cybertools.loni.org
www.storkproject.org
www.cct.lsu.edu
Questions?
Mehmet Balman balman@cct.lsu.edu

50. Thank you

51. Average Throughput of Concurrent Transfer
Jobs

52. Average Throughput of Concurrent Transfer
Jobs