Iomega Automatic Backup Pro Software Delivers Impressive Compression Results

Transcription

1 Technical White Paper March 2004 Iomega Automatic Backup Pro Software Delivers Impressive Compression Results Iomega REV Drive Achieves up to 2.6:1 Data Compression with Bundled IAB Pro Software Introduction The Calgary Corpus Data Set Results of IAB 2.0 Pro Testing How to Reproduce the Results Conclusion Appendix

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3 Introduction Iomega s revolutionary Removable Rigid Disk (RRD) technology provides the speed, reliability, and ease-of-use of a hard drive with the portability and expandability of tape and optical media. While based on standard hard drive components, the removable Iomega RRD disk contains only the magnetic media and spindle hub and motor for greater durability all the sensitive drive heads and electronics remain in the drive itself. Both the drive and disks are sealed by a unique shutter mechanism designed to keep the heads and media in a virtual clean room environment. Advanced air filtration, automatic head cleaning, and robust two-stage error correction are employed to ensure high data integrity and reliability. The Iomega REV 35GB/90GB * drive system is the first of the company s RRD-based family of products. With its high speed, capacity, and removable media, the Iomega REV products are the ideal solution for desktop and server-level backup as well as high-capacity, portable storage applications. This paper discusses the kinds of software compression that can be achieved with Iomega Automatic Backup Pro (IAB Pro) software. While most entry-level and low-end tape devices advertise compression ratios of 2:1, only a few can claim the 2.6:1 ratio that IAB Pro delivers. To prove these claims, the IAB Pro was tested using the Calgary Corpus data set on a freshly formatted drive and backed up using IAB Pro s system backup option with the Iomega REV drive as the destination drive. The results verify that the capacity of the REV drive is 35GB native and 90GB compressed, where compressed capacity is achieved assuming 2.6:1 data compression with the high setting on IAB Pro software. As always, this capacity may vary since compression is data and software dependent. The Calgary Corpus Data Set Data compression is inherently dependent on the type of data being compressed. Some file types respond very favorably to compression, while others are already stored in a more-or-less efficient or compressed state. As a result, predefined test data suites have been developed by independent sources to use as reference standards for use in the text compression community. One such independently developed data set, developed by Ian Witten and Tim Bell while visiting the University of Calgary in Alberta, Canada, is the Calgary Text Compression Corpus, also referred to as the Calgary Corpus data set. The Calgary Corpus data set consists of nine different types of text. To confirm that the performance of the different schemes is consistent for any given type, many of the types have more than one representation in * Compressed capacity assuming 2.6:1 data compression with high compression on Iomega Automatic Backup Pro software. Capacity may vary and is data and software dependent. 1

4 the data set. Standard English, both fiction and non-fiction, is represented by books and papers (labeled book1, book2, paper1, paper2, paper3, paper4, paper5, paper6). More unusual styles of English are found in a bibliography (bib) and a batch of unedited news articles (news). Three computer programs represent artificial languages (progc, progl, progp). A transcript of a terminal session (trans) is included to indicate the increase in speed that could be achieved by applying compression to a slow line to a terminal. All of the files mentioned above use ASCII encoding. Some non-ascii files are also included: two files of executable code (obj1, obj2), some geophysical data (geo) and a bit-map black-and-white picture (pic). The file called geo is particularly difficult to compress because of a wide range of data values, while the file pic is highly compressible because of large amounts of white space represented by long runs of zeros. The Corpus Data Set can be found at: ftp://ftp.cpsc.ucalgary.ca/pub/projects/text.compression.corpus Results of IAB 2.0 Pro Testing Testing the Calgary Corpus data set on IAB Pro backing up to an Iomega REV drive using the high compression setting in the software yielded 2.6:1 compression results with a 1.8GB data set and 2.7:1 compression results with a 5GB data set. The results are summarized in the table below. Compression ratios achieved with high compression setting in IAB Pro: Capacity of Calgary Corpus Data Set Compression Ratio Results 1.8 GB set 2.7:1 5.0 GB set 2.7:1 These results were achieved using the system outlined in Appendix A. How to Reproduce the Results In order to reproduce the results stated above, a copy of the Calgary Corpus data set is required along with an empty hard drive and copy of IAB Pro. To ensure that the drive is truly empty, it should be formatted before starting the test. The first step involves creating a folder on the now-empty drive and copying the Calgary Corpus test suite into the folder. In order to create the 1.8GB data set, the Calgary Corpus is copied 597 more times. In order to create the 5GB data set, the Calgary Corpus is copied 1,661 more times. The second step entails launching the IAB Pro application and then selecting the system backup option. The third step involves working with the IAB 2.0 wizard to select the correct volume, which contains copies of the Calgary Corpus. The fourth step is choosing the option to keep the 2

5 backup in a compressed image file and then selecting the high compression ratio. In order to determine the compression ratio, rightclick on the drive that contains the original Calgary Corpus data and record the used space in bytes. This same procedure needs to be followed for the drive which contains the compressed image, which is the IAB Pro destination. The calculations are computed by dividing the used bytes of the destination by the used bytes of the source and then taking the inverse of this number to achieve the compression ratio for this set. Conclusion This paper outlines how Iomega is able to replicate the outstanding 2.6:1 software compression ratio using IAB Pro on the Calgary Corpus data set. Using IAB Pro s high compression option, the possible results are all at least 2.6:1 compression, making it among the best product choices for its particular market segment. Please be aware that actual compression on any data set other than the Calgary Corpus or using a drive other than an Iomega REV drive is likely to cause variations from the results set forth above. After all, compression results are strictly dependant upon both the drive used and the data being compressed, among many other factors. The efforts explained reflect honest testing on actual drive specimens, but as noted above, other drives from various manufacturers using different types of data may yield different results. # # # This information is to be considered preliminary and subject to change. Please be aware that Iomega makes no commitment to update or revise this document in the future, and does not imply any representation, guarantee, or warranty by this document. This document does not create any contractual rights. 3

6 Appendix A System Specification for IAB Pro Compression Test The 1.8GB set consisted of 1,875,548,334 bytes on the source and 682,653,922 bytes on the destination resulting on a compression ratio of 2.747:1 The 5GB set consisted of 5,218,234,142 bytes on the source and 1,899,308,130 bytes on the destination resulting in a compression ratio of 2.747:1 These test were performed on a Dell Latitude C400, Pentium III 789 MHz CPU, 1.00 GB of RAM 4