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28 .\" @(#)equip.ms 6.2 (Berkeley) 4/16/91
34 Various combinations of the three manufacturers disk controllers,
35 and two pairs of Winchester disk drives were tested on both
36 VAX 11/780 and VAX 11/750 CPUs. The Emulex and Systems Industries
37 disk controllers were interfaced to Fujitsu 2351A
39 404 Megabyte disk drives.
40 The DEC UDA50 disk controller was interfaced to two DEC RA81
41 456 Megabyte Winchester disk drives.
42 All three controllers were tested on the VAX 780 although
43 only the Emulex and DEC controllers were benchmarked on the VAX 11/750.
44 Systems Industries makes a VAX 11/750 CMI interface for
45 their controller, but we did not have time to test this device.
46 In addition, not all the storage systems were tested for
48 Each of the controllers and disk drives used in the benchmarks
49 is described briefly below.
51 DEC UDA50 disk controller
53 This is a new controller design which is part of a larger, long range
54 storage architecture referred to as
56 or \fBD\fRigital \fBS\fRtorage \fBA\fRrchetecture.
57 An important aspect of DSA is migrating a large part
58 of the storage management previously handled in the operating
59 system to the storage system. Thus, the UDA50 is a much more
60 intelligent controller than previous interfaces like the RH750 or
62 The UDA50 handles all error correction.
63 It also deals with most of the physical storage parameters.
64 Typically, system software requests a logical block or
66 The physical locations of these blocks,
67 their head, track, and cylinder indices,
68 are determined by the controller.
69 The UDA50 also orders disk requests to maximize throughput
70 where possible, minimizing total seek and rotational delays.
71 Where multiple drives are attached to a single controller,
72 the UDA50 can interleave
74 data transfers from multiple drives.
76 The UDA50 is a UNIBUS implementation of a DSA controller.
77 It contains 52 sectors of internal buffering to minimize
78 the effects of a slow UNIBUS such as the one on the VAX-11/780.
79 This buffering also minimizes the effects of contention with
80 other UNIBUS peripherals.
82 Emulex SC750/SC780 disk controllers
84 These two models of the same controller interface to the CMI bus
85 of a VAX 11/750 and the SBI bus of a 11/VAX 780, respectively.
86 To the operating system, they emulate either an RH750 or
88 The controllers install in the
90 locations in the CPU cabinets and operate from the
94 or \fBS\fRtorage \fBM\fRodule \fBD\fRrive
95 interface to the disk drives.
96 Although a large number of disk drives use this interface, we tested
97 the controller exclusively connected to Fujitsu 2351A disks.
99 The controller ws first implemented for the VAX-11/750 as the SC750
100 model several years ago. Although the SC780 was introduced more
101 recently, both are stable products with no bugs known to us.
103 System Industries 9900 disk controller
105 This controller is an evolution of the S.I. 9400 first introduced
106 as a UNIBUS SMD interface.
107 The 9900 has been enhanced to include an interface to the VAX 11/780 native
109 It has also been upgraded to operate with higher data rate drives such
110 as the Fujitsu 2351As we used in this test.
111 The controller is contained in its own rack-mounted drawer with an integral
113 The interface to the SMD is a four module set which mounts in a
114 CPU cabinet slot normally occupied by an RH780.
115 The SBI interface derives power from the VAX CPU cabinet power
120 The RA81 is a rack-mountable 456 Megabyte (formatted) Winchester
121 disk drive manufactured by DEC.
122 It includes a great deal of technology which is an integral part
123 of the DEC \fBDSA\fR scheme.
124 The novel technology includes a serial packet based communications
125 protocol with the controller over a pair of mini-coaxial cables.
126 The physical characteristics of the RA81 are shown in the
133 DEC RA81 Disk Drive Characteristics
135 Peak Transfer Rate 2.2 Mbytes/sec.
136 Rotational Speed 3,600 RPM
137 Data Sectors/Track 51
138 Logical Cylinders 1,248
139 Logical Data Heads 14
140 Data Capacity 456 Mbytes
141 Minimum Seek Time 6 milliseconds
142 Average Seek Time 28 milliseconds
143 Maximum Seek Time 52 milliseconds
147 Fujitsu 2351A disk drives
149 The Fujitsu 2351A disk drive is a Winchester disk drive
150 with an SMD controller interface.
151 Fujitsu has developed a very good reputation for
152 reliable storage products over the last several years.
153 The 2351A has the following physical characteristics:
159 Fujitsu 2351A Disk Drive Characteristics
161 Peak Transfer Rate 1.859 Mbytes/sec.
162 Rotational Speed 3,961 RPM
163 Data Sectors/Track 48
166 Data Capacity 404 Mbytes
167 Minimum Seek Time 5 milliseconds
168 Average Seek Time 18 milliseconds
169 Maximum Seek Time 35 milliseconds