Space Data: Information on Data Storage Technologies

Published by the Government Accountability Office on 1990-09-12.

Below is a raw (and likely hideous) rendition of the original report. (PDF)

                                                                             - ’ &.
                           United   States   General   Accounting   Office

                           Fact Sheet for the Chairman,
                           Subcommittee on Science, Technology,
                           and Space, Committee on Commerce,
                           Science, and Transportation,
                           U.S. Senate
September   1990
                           Information on Data
                           Storage Technologies                                   r

                    RESTRICTED --Not     to be released outside the
                    General Accounting Once unless specifically
                    approved by the OfRce of Congressional

      United States
GAO   General Accounting  Office
      Washington, D.C. 20648

      Information      Management         and
      Technology      Division


      September 12, 1990

      The Honorable Albert Gore, Jr.
      Chairman, Subcommittee on Science,
        Technology, and Space
      Committee on Commerce, Science,
        and Transportation
      United States Senate

      Dear Mr. Chairman:

      As requested by your office, we are providing information on current
      and advanced data storage technologies to assist the committee in evalu-
      ating their potential use for the National Aeronautics and Space Admin-
      istration’s (NASA) future storage needs. Specifically, you requested that
      we identify the general characteristics and costs of these data storage
      technologies. In a future report we will furnish information on NASA'S
      plans for using and applying these technologies to store the large
      amounts of space science data expected from the growing number of
      missions scheduled for the 1990s.

      The National Aeronautics and Space Act of 19681 placed responsibility
      on NASA for conducting space exploration research that contributes to
      the expansion of human knowledge and directed it to provide the widest
      practicable and appropriate dissemination of this information. Since
      1968 NASA has spent more than $24 billion on space science to help us
      understand our planet, solar system, and the universe. It has launched
      over 260 mJor space science missions and has acquired massive
      volumes of data. The majority of data from these past missions is stored
      on at least 1.2 million magnetic tapes, which have the capacity to store
      over 90 billion pages of text.*

      NASA anticipates the volume of data generated and stored for future mis-
      sions will be unparalleled in the history of the agency. It estimates that
      the annual volume of archived data will rise from 63 terabiW in 1990 to
      more than 4,200 terabits by the late lQQOs-more than a 6,500-percent

      ‘Public Law S-668.

      ‘This estimate is based on the storage capacity of a standard 2,4OO-foot-longtape, with data stored at
      6,250 bits per inch. A single page of text contains about 400 words, with 6 characters per word-or
      about 19,200 bits of data.

      “One terabit of data is approximately 10’” bits (or 1 trillion bits). About 700 high-density tapes 1ti.%O
      bits per inch) would be required to store 1 terabit of data.

      Page 1                                 GA0/IMTEC88F’S
                                                     Lhta Storage Technologies                      and NASA

                                         jump. Figure 1 shows the expected increase in data volumes through the

Figure 1: NASA’s Estimated Annual Data
                                         4500 Tuablta or Dam

                                         Storing such large volumes of data will require new and more efficient
                                         data-storage media. In the past few years large strides have been made
                                         in both magnetic tape and optical disk technologies with the commercial
                                         introduction of higher capacity tape and optical media. Appendix I
                                         briefly explains several commercially available data storage technolo-
                                         gies. The choice of a data-storage medium depends on the amount of
                                         data to be archived, the storage capacity of the medium, and the cost of
                                         the medium and supporting equipment needed to access it. Appendix II
                                         presents several general performance and archiving characteristics of
                                         data-storage technologies. Appendix III presents a detailed breakdown
                                         of costs.

                                         The information in this report was obtained from manufacturers’ speci-
                                         fications, available literature, and discussions with NASA officials and
                                         other experts. Our work was conducted between December 1989 and

                                         Page 2                     GAO/JMTEG8O-9SR3
                                                                                  Da- Stomge Technologies and NASA

July 1990. We discussed the contents of this report with NASA headquar-
ters, Jet Propulsion Laboratory, and Goddard Space Flight Center offi-
cials, and have incorporated their comments where appropriate. Details
of our objectives, scope, and methodology appear in appendix IV.

As  arranged with your office, unless you publicly announce the contents
of this report earlier, we plan no further distribution of it until 30 days
from the date of this letter. At that time we will send copies to other
appropriate congressional committees; the Administrator, NASA; and
other interested parties. We will also make copies available to others
upon request.

This work was performed under the direction of Samuel W. Rowlin,
Director, Defense and Security Information Systems, who can be
reached at (202) 275-4649. Other major contributors are listed in
appendix V.

Sincerely yours,

Ralph V. Carlone
Assistant Comptroller General

 P8ge 3

Letter                                                                                              1

Appendix I                                                                                          6
Definitions of Data-
Storage Technologies
Appendix II
Appendix III                                                                                    16
Costs of the
Appendix IV                                                                                     17
Objectives, Scope,and
Appendix V                                                                                      19
Major Contributors to
This Report
Figures                 Figure   1: NASA’s Estimated Annual Data Volume                          2
                        Figure   I. 1: Magnetic Reel                                             6
                        Figure   1.2: 34800mpatible                                              7
                        Figure   1.3: Helical Scan, 4mm                                          8
                        Figure   1.4: Compact Disk-Read Only Memory                              9
                        Figure   1.5: Write Once Read Many                                      10
                        Figure   1.6: Rewritable Optical Disk                                   11
                        Figure   1.7: Optical Tape                                              12

                        P8ge 4                     GAO/‘lMTEC~~   Lhta Storage Technologka and WA


CD-ROM     compact disk-read only memory
DAT        digital audio tape
GAO        General Accounting Office
GB         gigabyte
IMTJX      Information Management and Technology Division
MB         megabyte
NASA       National Aeronautics and Space Administration
WORM       write once read many

Page 6                     GAO/‘IMTEG~Fs   Data Storage Technolo&s   and ?iASA
Appendix I

Definitions of DataStorage Technologies

                            The following is a brief description of seven data-storage technologies
                            that were commercially available when we did our work. The figures
                            used to portray each technology were provided by several manufac-
                            turers and used with their permission. Their use, however, does not
                            imply an approval or endorsement of the manufacturers or their prod-
                            ucts by us.

Magnetic Reel               One-half-inch wide, reusable, 9-track magnetic tape. Data are written
                            horizontally on the tape and wound on reels. Tape is considered a
                            sequential-access medium, i.e., data records are accessed one after the
                            other, in the order in which they are physically stored on the tape.

Figure 1.1: Magnetic Reel

                            Source: Ampex Corporation.

                            Page 6                       GAO/lMTEG9048Fs   Data storage Technologies and NA!SA
                              Appendix I
                              Definitions of DataStorage Tehnologks

3480-Compatible               One-half-inch wide, reusable, l&track magnetic tape, stored in car-
                              tridges. Data are written horizontally on the tape. This is a sequential-
                              access medium.

Figure 1.2: 3480-Compatible

                              Source: Fujitsu America, Inc.

                              Page 7                           GAO/lMTEG9O-8SFs
                                                                       Data Stmage Te&nologies    and SASA
                              Appendix I
                              Deflnltlona of DataStmage Technologh

Helical Scan                  This technology uses a rotating head to write data diagonally on reus-
                              able magnetic tape. The most common tape sizes are 8 millimeter (mm)
                              tape and 4mm digital audio tape (DAT). Helical scan is a sequential-access

Figure 1.3:Helled Scan, 4mm


                              Source: Sony Corporation   of America.

                              Page 8                                   GAO/lMTEC9o4gFs   Data Storage Technologies and NASA
                                                         L-L----.------------   __...“-.___   ____---
__L_I_C_C_____-_I-I---   + __ . I __ “I_c-----
                            Aj~~reni’ix ‘.
                            Dtllnjrmns of Iw~Stxrage’ieeaw~rgies
                                  AppendLx I
                                  Definitions of DataStorage Technologies

Write Once Read Many              The WORM is an optical disk on which data are written by laser. The disk
                                  can only be written on once and is accessed randomly.
Figure 1.5:Write Once Read Many

                                  Source: Panasonic Commumcations   and Systems Company, Division of Matsushita Electric Corporation
                                  of America.

                                   Page 10                             GAO/JMTEC9O-SSFs Data Storage Technologies and NASA
                                     Appendix I
                                     Definitions of Data&m-age Technologies

Rewritable Optical Disk              A magneto-optical disk that combines magnetic and optical (laser)
                                     recording technologies. The disk can be written on many times and is
                                     accessed randomly.

Figure 1.6:Rewritable Optical Disk

                                     Source: Sony Corporation   of America.

                                      Page 11                                 GAO/IMTEG9OJ38FS
                                                                                      Data Storage Technologies   and NASA
                          Appendix I
                          Defhltlons of Data&mage   Technologies

Optical Tape              A product made from digital paper, a thin flexible film manufactured in
                          large rolls and cut into many shapes and sizes. Data are written once by
                          laser on a nonreusable tape. This is a sequential-access medium.

Figure 1.7:Optical Tape

                          Source: Cl Imagedata.

                          Page 12                           GAO-m      Data Storage Technologies and NASA
Page 13   GAO-H   Daa Stomge Technologies nnd NASA
Appendix II

General Characteristicsa


                Characteristic                      Magnetic reel    3480~compatibleb
                Storage capacity                    Low              Low
                                                    .09-.2GB          2GB
                Access time                         High             Med
                                                    l-5 mm           13-25 set
                Transfer rate                       Low/Mod          Med/High
                (per second)
                                                    .3-l .25MB       1S-4 5MB
                Storage lifeC                       Low              Low
                                                    3-10 yrs         3-10 yrs
                Bit error rate                      Hlgh             Low/High
                                                    10-10            10-13. ,0-l,
                Format standards?                   Yes              Yea
                Mature technoloav?                  Yea              Yes

                Page 14              GAO/lMTEC3O-t3SFS Data Stirage Techmhgb        ud   WA
                                         Appendix Il
                                         General       Characteri8tlC3

                                                                                                                      Rewritable           Optical
Helical 4mm (DA77   Helical 6mm   CD-ROM                   WORM 5.25”        WORM 12”            WORM 14”             optical disk         taoe
High                High          MOd                      Mod               High                High                 Med                  High
1.3GB               2-5GB         .5-,808                   .6-.9GB          2-6GB               7-8GB                .6-l GB              1OOOGB
Med                 High          Low                      Low               Low                 Low                  Low                  Mod
20 set              10 min        150-800 ms               60-250 ms         145-250 ms          9-700 ms             35-95 ms             28 set
Low                 Low           Low                      Low/Med           Low                 MOd                  Low/Mod              High
.2MB                .5MB          .15MB                     .3-l .3MB        .3-.8MB             1MB                   15-l .5MB           3MB
Low                 Low           Med/High                 Med               MOd                 Med                  Med                  Med
3-10 vrs            3-10 vrs      20-100 yrs                1O-30 yrs        1O-30 yrs           1O-30 yrs            lO+ yrs              15+ vrs
Low                 Low           MOd                      MOd               Med                 MOd                  Med                  Med
10-15               10-13         10-Q                      10-Q             10-12               10-12                1o-12                10-12
No                  No            Yes                      No                No                  No                   No                   No
No                  No            Yes                      No                No                  No                   No                   No

                                         Wanufacturer specifications were used as the information source in most cases. The actual. effective
                                         values may be different. For example, the bit error rate does not include errors caused by hardware or
                                         handling problems. Transfer rates have been reported by some users to be as low as half of what
                                         manufacturers claim.
                                         b‘rhere are two versions of 34&l drives.

                                         cOpttcal technologies have not been commercially      available for data storage long enough to know ‘f
                                         they will meet the claims for storage life.


                                         Storage capacity: the amount of data that can be stored on the medium, measured In glgabytes (GB) A
                                         gigabyte is approximately one billion bytes of data, and one byte IS 8 data btts. For archIving, higher
                                         capacity is Important for storing a high volume of data.
                                         Access time: the interval between a request to read or store data and the completton of that task Time
                                         is measured in mrnutes (min), seconds (set). or milliseconds (ms). A mtllisecond IS one thousandth of a
                                         second. For archiving, access time IS less important than other charactenstcs.
                                         Transfer rate: the rate at which data are transferred from the drive to the computer, measured In
                                         megabytes &IS) per second. A megabyte is one million bytes of data. For archiving, a high transfer rate
                                         IS important when frequent requests or large volumes of data must be accessed from storage
                                         Stora e life: the period of time data will remain usable given reasonable care and maintenance of the
                                         m ia or archiving,
                                         -a-%-             ”     media with a long storage life reduces the frequency of recopying the data over
                                         Bit error rate: the probability of a bit of data delivered from the device being Incorrect. For archtvlng. it IS
                                         important that data that will be stored for future reference and analysis be correct and therefore have a
                                         low bit error rate.
                                         Format standards: rules describing how the data are stored. For archiving, format standards are espe-
                                         cially important because the data will be used over a long penod of time, probably by many users
                                         Mature tecl7nology: a technology that is readily availabte on the commercial market and that has been In
                                         operattona use In many Installations over a substantial period of time. For archiving, a mature medium IS
                                         important to ensure that It can be kept and read easily and accurately over a long penod of time

                                         P8ge 16                                     GAO/IblTEGllO433F’S Data Storage Technologies and ?USA
Appendix III

Costs of the Technologiesa

                                                                         coa per         Modla unit
               Technolom                                               mwtabyteb              cow                 Drive cost
               Maanetic reel                                            $0.1 l-.16          $14-21         WlOO-20,000
               3460-compatibled                                            .03-08             6-16         15,ooo-90,ooo
               Helical   4mm                                               .02-.03           20-35            4,00+7,000
               Helical 8mm                                              .003-,008             6-40            3,000-7,000
               CD-ROM                                                                  1500 master/
                                                                           .02-.20           2 COPY            4453,695
               WORM 5.25”                                                  .ll-33           65-298          2,500-10,000
               WORM 12”                                                    .07-.17         346-400         13,000-17,000
               WORM 14”                                                    .07-.09              595                25,000
               Rewritable optical    disk                                  .42-.65         249-650          4,50+10,950
               Ootical taDe                                                      .Ol         10.000               200.000
               aThese figures are for comparison purposes only. Wa limited our review to the media and drive costs.
               Other hardware and software to access and use the storage medium would be needed, dependrng on
               the technology selected. For example, one large mass storage system we identrfied included a
               supercomputer, numerous user workstations, an operations workstation, magnetic disks, printers, a
               local area network, and a smaller computer known as a file server, which essenttally permrts compo-
               nents of the system to access the mass storage system.

               bThe cost per megabyte was calculated by divrding the minimum cost for the storage technology (drsk,
               tape, etc.) by the mmimum capacity for the low end of the range, and dividing the maximum cost and
               capacity for the high end of the range.

               CThis represents the cost for one unit of storage media, i.e., one tape reel, cartridge, or disk
               dThere are two classes of 3480 drives: large, and the smaller “rack mountable”      versron. The low-end
               pricing IS for the smaller version, and high end for the larger versron.

                Page 16                                  GAO/JMTEC9O&Wf3 Data Storage Tednologks                    and NASA

&y&ves,   Scope,and Methodology

              The Subcommittee on Science, Technology, and Space, Senate Committee
              on Commerce, Science, and Transportation, asked us to identify (1) rele-
              vant advanced data storage technologies, including their strengths,
              weaknesses, and costs; (2) current NASAinitiatives in this area; and (3)
              major agency programs that may benefit from the use of these technolo-
              gies. As agreed in a subsequent meeting with the Subcommittee, this
              report provides information on the first area, relevant technologies and
              their attributes, in summary form; information on the second and third
              areas will be presented in a follow-up report.

              Information on the estimated volumes of data to be generated through
              the year 2000 was obtained from the NASA Office of Space Science and

              To identify and describe applicable data storage technologies, we

              conducted a literature search of articles describing advanced data
              archiving technologies;
              contacted manufacturers of advanced data archiving technologies to
              obtain product background and specifications;
              reviewed NASA studies, reports, and other documents related to data
              management prepared by various scientific groups and committees;
              interviewed NASA, Jet Propulsion Laboratory, and Goddard Space Plight
              Center officials (including National Space Science Data Center officials)
              responsible for managing and overseeing NASA'S data;
              conferred with data storage media experts; and
              attended a symposium on mass storage systems sponsored by the Insti-
              tute of Electrical and Electronics Engineers.

              We reviewed articles in the literature and studies as a basis for identi-
              fying relevant data-storage technologies. We limited inclusion to those
              technologies that were available commercially and capable of handling
              large volumes of data.

              Characteristics and cost information on each technology was gathered
              from all sources identified above, and inconsistencies in reported attrib-
              utes were resolved. Manufacturers’ specifications were used as a pri-
              mary data source. Information on technology performance was accepted
              as provided; no testing of equipment was done to verify the accuracy of
              manufacturers’ claims or other reports of performance.

              To compare the costs of the various technologies we obtained price
              information on the media and the drive required to access the data. An

              Page 17                      GAO/IMTEGOO-&l~   Data Stmage Technologies and USA
actual storage system requires much more than these components; how-
ever, the wide variety of ways in which a complete storage system could
be assembled limited us from providing cost information on complete

Experts in data archiving, data processing, magnetic media, and space
data storage reviewed our technology definitions and attributes for their
accuracy and appropriateness.

Our audit work was performed in accordance with generally accepted
government auditing standards, between December 1989 and July 1990,
at various locations including NASA headquarters in Washington, D.C.;
the Goddard Space Flight Center in Greenbelt, Maryland; and the Jet
Propulsion Laboratory in Pasadena, California.

Page 18                     GAO/IMTEC9O-SSFs
                                    D&A Storrge Technologies      and NASA
Appendix V

Major Conttibutors to This Report

                       Ronald W. Beers, Assistant Director
Information            Yvette Ramos, Staff Evaluator
Management and
Technology Division,
Washington, DC.

Los Angeles Regional   George Vindigni, Evaluator-in-Charge
Office                 Monica L. Kelly, Staff Evaluator
                       James D. Nolan, Staff Evaluator
                       Shawnalynn R. Smith, Staff Evaluator

(aloaoz)               Page 19                     GAO/LMl’EG@6.88F’S
                                                           Data Stomge Technobgk- ud   WA
Ordering   Information

The fast five copies of each GAO report are free. Additional  copies
are $2 each. Orders should be sent to the following address, accom-
panied by a check or money order made out to the Superintendent
of Documents, when necessary. Orders for 100 or more copies to be
mailed to a single address are discounted 25 percent.

U.S. General Accounting Office
P.O. Box 6015
Gaithersburg, MD 20877

Orders may also be placed by calling   (202) 2756241.

   --.       _.,
United States
General Accounting    Office
Washington,   D.C. 20548

Official   Business
Penalty    for Private   Use $300