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diff --git a/share/doc/papers/diskperf/motivation.ms b/share/doc/papers/diskperf/motivation.ms new file mode 100644 index 00000000000..2884fc59f52 --- /dev/null +++ b/share/doc/papers/diskperf/motivation.ms @@ -0,0 +1,93 @@ +.\" Copyright (c) 1983 The Regents of the University of California. +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)motivation.ms 6.2 (Berkeley) 4/16/91 +.\" +.ds RH Motivation +.NH +Motivation +.PP +These benchmarks were performed for several reasons. +Foremost was our desire to obtain guideline to aid +in choosing one the most expensive components of any +VAX UNIX configuration, the disk storage system. +The range of choices in this area has increased dramatically +in the last year. +DEC has become, with the introduction of the UDA50/RA81 system, +cost competitive +in the area of disk storage for the first time. +Emulex's entry into the VAX 11/780 SBI controller +field, the SC780, represented a important choice for us to examine, given +our previous success with their VAX 11/750 SC750 controller and +their UNIBUS controllers. +The Fujitsu 2351A +Winchester disk drive represents the lowest cost-per-byte disk storage +known to us. +In addition, Fujitsu's reputation for reliability was appealing. +The many attractive aspects of these components justified a more +careful examination of their performance aspects under UNIX. +.PP +In addition to the direct motivation of developing an effective +choice of storage systems, we hoped to gain more insight into +VAX UNIX file system and I/O performance in general. +What generic characteristics of I/O subsystems are most +important? +How important is the location of the controller on the SBI/CMI versus +the UNIBUS? +Is extensive buffering in the controller essential or even important? +How much can be gained by putting more of the storage system +management and optimization function in the controller as +DEC does with the UDA50? +.PP +We also wanted to resolve particular speculation about the value of +storage system optimization by a controller in a UNIX +environment. +Is the access optimization as effective as that already provided +by the existing 4.2BSD UNIX device handlers for traditional disks? +VMS disk handlers do no seek optimization. +This gives the UDA50 controller an advantage over other controllers +under VMS which is not likely to be as important to UNIX. +Are there penalties associated with greater intelligence in the controller? +.PP +A third and last reason for evaluating this equipment is comparable +to the proverbial mountain climbers answer when asked why he climbs +a particular mountain, +``It was there.'' +In our case the equipment +was there. +We were lucky enough to assemble all the desired disks and controllers +and get them installed on a temporarily idle VAX 11/780. +This got us started collecting data. +Although many of the tests were later rerun on a variety of other systems, +this initial test bed was essential for working out the testing bugs +and getting our feet wet. +.ds RH Equipment +.bp |