TIFF to JPEG2000 Migration Experiment at ONB

Investigator(s)

Sven Schlarb

Dataset

Austrian National Library Tresor Music Collection

Platform

Purpose of this experiment

The purpose of this experiment is to evaluate the performance of a scalable workflow for migrating TIFF images to images in the JPEG2000 format compared to an equivalent Taverna version of the workflow processing the data sequentially.

Evaluation method

A Taverna workflow for sequential processing serves as a reference point for the large-scale execution. Out of the full Austrian National Library Tresor Music Collection data set subsets of increasing size are selected by a random process.

The following bash statement prepends a random number and subsequently orders the list to extract a random sample from the full data set:

The resulting file contains the local file paths and can be used as input for the Taverna workflow presented in the next section.

Additionally the files are uploaded to HDFS as input for the large-scale workflow execution.

By that way it is possible to compare the sequential execution time to the large-scale processing time. The results depend on the size and configuration of the Hadoop cluster, therefore the relation between sequential and large-scale processing is expressed by the "parallelisation efficiency" which is the sequential execution time, divided by the distributed execution time, and again divided by the number of nodes available for parallel processing:

Taverna workflow - sequential processing

The proof-of-concept version of the TIFF to JPEG2000 image migration workflow with quality assurance was created as a Taverna workflow illustrated by the following workflow diagram:

Diagram of the TIFF to JPEG2000 image migration workflow, Workflow available on MyExperiment at http://www.myexperiment.org/workflows/4276.html
The Taverna workflow reads a textfile containing absolute paths to TIF image files and converts them to JP2 image files using OpenJPEG (https://code.google.com/p/openjpeg).

Based on the input text file, the workflow creates a Taverna list to be processed file by file. A temporary directory is created (createtmpdir) where the migrated image files and some temporary tool outputs are stored.

Before starting the actual migration, it is checked if the TIF input images are valid file format instances using Fits (https://code.google.com/p/fits, JHove2 under the hood, http://www.jhove2.org). An XPath service is used to extract the validity information from the XML-based Fits validation report.

If the images are valid TIF images, they are migrated to the JPEG2000 (JP2) image file format using OpenJPEG 2.0 (opj_compress).

Subsequently, it is again checked if the migrated images are valid JP2 images using SCAPE tool Jpylyzer (http://www.openplanetsfoundation.org/software/jpylyzer). An XPath service (XPathJpylyzer) is used to extract the validity information from the XML-based Jpylyzer validation report.

Finally, we verify if the migrated JP2 images are valid surrogates of the original TIF images by restoring the original TIF image from the converted JP2 image and comparing whether original and restored images are identical.

The sequential execution of this workflow is used as a reference point for measuring the parallelisation efficiency of the scalable version and it allows measuring how the processing times of the different components compare to each other.

The following diagram shows the average execution time of each component of the workflow in seconds and was created from a 1000 images sample of the Austrian National Library Tresor Music Collection:

SCAPE Platform workflow - distributed processing

Apache Pig was used to create a scalable version of this workflow. The different processing steps of the Taverna workflow for sequential processing are represented by Pig Latin statements.

The comments of each processing step In the script below indicate which is the corresponding processing component in the Taverna workflow.

Evaluation summary

Files := Size of random sample

Total GB := Total size in Gigabytes

Secs := Processing time in seconds

Mins := Processing time in minutes

Hrs := Processing time in hours

Afg.p.f. := Average processing time per file in seconds

Obj/h := Number of objects processed per hour

GB/min := Throughput in Gigabytes per minute

GB/min := Throughput in Gigabytes per hour

Err := Number of processing errors

Par.Eff. := Parallelisation efficiency (sequential execution time, divided by the distributed execution time, and again divided by the number of nodes available for parallel processing)

Taverna Workflow - Sequential execution

Files	Total GB	Secs	Mins	Hrs	Avg.p.f.	Obj/h	GB/min	GB/h	Err
5	0,31 GB	179	2,98	0,05	35,80	101	0,10	6,22	0
7	0,89 GB	438	7,30	0,12	62,57	58	0,12	7,29	0
10	0,90 GB	478	7,97	0,13	47,80	75	0,11	6,8	0
20	2,23 GB	1150	19,17	0,32	57,50	63	0,12	6,98	0
30	2,99 GB	1541	25,68	0,43	51,37	70	0,12	6,98	0
40	3,60 GB	1900	31,67	0,53	47,50	76	0,11	6,81	0
50	3,46 GB	2039	33,98	0,57	40,78	88	0,10	6,1	0
75	6,05 GB	3425	57,08	0,95	45,67	79	0,11	6,36	0
100	8,30 GB	4693	78,22	1,30	46,93	77	0,11	6,37	0
200	15,19 GB	9246	154,10	2,57	46,23	78	0,10	5,91	0
300	19,07 GB	11773	196,22	3,27	39,24	92	0,10	5,830538247	0
400	24,78 GB	15644	260,73	4,35	39,11	92	0,10	5,702311971	0
500	34,55 GB	21345	355,75	5,93	42,69	84	0,10	5,826842116	0
750	63,07 GB	37397	623,28	10,39	49,86	72	0,10	6,07104919	0
1000	71,82 GB	42376	706,27	11,77	42,38	85	0,10	6,101491294	0
2000	139,00 GB	84938	1415,63	23,59	42,47	85	0,10	5,891372268	0
3000	211,85 GB	128959	2149,32	35,82	42,99	84	0,10	5,913838368	0

Pig Workflow - Distributed Execution

Files	Total GB	Secs	Mins	Hrs	Avg.p.f.	Obj/h	GB/min	GB/h	Err	Par.Eff.
5	0,31 GB	96	1,60	0,03	19,20	188	0,19	11,60	0	7,46%
7	0,89 GB	101	1,68	0,03	14,43	250	0,53	31,64	0	17,35%
10	0,90 GB	103	1,72	0,03	10,30	350	0,53	31,56	0	18,56%
20	2,23 GB	114	1,90	0,03	5,70	632	1,17	70,45	0	40,35%
30	2,99 GB	138	2,30	0,04	4,60	783	1,30	77,99	0	44,67%
40	3,60 GB	161	2,68	0,04	4,03	894	1,34	80,41	0	47,20%
50	3,46 GB	183	3,05	0,05	3,66	984	1,13	68,01	0	44,57%
75	6,05 GB	272	4,53	0,08	3,63	993	1,34	80,11	0	50,37%
100	8,30 GB	373	6,22	0,10	3,73	965	1,34	80,15	0	50,33%
200	15,19 GB	669	11,15	0,19	3,35	1076	1,36	81,73	0	55,28%
300	19,07 GB	808	13,47	0,22	2,69	1337	1,42	84,95	0	58,28%
400	24,78 GB	1091	18,18	0,30	2,73	1320	1,36	81,77	0	57,36%
500	34,55 GB	1397	23,28	0,39	2,79	1288	1,48	89,03	0	61,12%
750	63,07 GB	2399	39,98	0,67	3,20	1125	1,58	94,64	0	62,35%
1000	71,82 GB	2746	45,77	0,76	2,75	1311	1,57	94,16	0	61,73%
2000	139,00 GB	5450	90,83	1,51	2,73	1321	1,53	91,82	0	62,34%
3000	211,85 GB	8328	138,80	2,31	2,78	1297	1,53	91,58	0	61,94%

The following diagram shows the comparison of wall clock times in seconds (y-axis) of the Taverna workflow and the Pig workflow using an increasing number of files (x-axis).