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es are in use track record increases the capacity of the disk by writing a single large record per track instead of using 20 separate sectors a track can hold 2 980 characters in 6 bit move mode and 2 682 7 bit characters in load mode giving the drive a total capacity of 17 880 000 bits in 6 bit mode and 18 774 000 bits in 7 bit mode 35 the master drives models 1 3 4 and 5 which contain extra power supplies and the control logic are about a foot wider than the model 2 slave drive ibm system 360 and other ibm mainframe hdds edit see also count key data and history of ibm ckd controllers ibm 2302 edit the ibm 2302 is the system 360 version of the 1302 with track formatting in accordance with s 360 dasd architecture rather than 7000 series architecture it uses a non removable module of 25 platters of which 46 surfaces are used for recording the 2302 model 3 contains one module and the model 4 two there are two independent access mechanisms per module one for the innermost 250 cylinders and one for the outermost 250 tracks available to each access mechanism are called an access group the access mechanism provides one read write head per track average rotational delay is 17 milliseconds msec and maximum is 34 msec maximum seek time per access group is 180 msec the track size is 4985 bytes with formatting information and alternate tracks module capacity is stated as 112 mb the 2302 attaches to ibm mainframes via a ibm 2841 storage control unit 36 ibm 2305 edit the ibm 2305 fixed head storage a fixed head disk drive sometimes incorrectly called a drum and associated ibm 2835 storage control 37 were announced in 1970 38 initially to connect to the 360 85 and 360 195 using the ibm 2880 block multiplexor channel the 2305 drive was in much demand when the system 370 offered virtual storage and these 2305s were often used for paging devices they were used in this way on 3155 3165 3158 3168 3033 4341 and 3081 with special feature microcode the 2305 was also used for high activity small data sets such as catalogs and job queues the 2305 1 runs at 3 0 mb second when attached using the 2 byte channel interface and the larger 2305 2 runs at 1 5 mb second 38 the 2305 provides large scale ibm computers with fast continuous access to small sized quantities of information its capacity and high data rate make it ideal for some systems residence functions work files job queues indices and data sets that are used repeatedly 38 its fast response time makes it attractive as a paging device in a heavily loaded systems where there are 1 5 or more transactions per second 39 ibm 2311 edit ibm 2311 disk storage drive with its six platters the ibm 2311 disk storage drive was introduced with the 2841 control unit in 1964 for use throughout the ibm system 360 the combination was also available on the ibm 1130 and the ibm 1800 the drive also directly attaches to the ibm system 360 model 20 and the ibm system 360 model 25 all drives used the ibm 1316 disk pack introduced with the ibm 1311 the 2311 model 1 attaches to most ibm mainframes through a 2841 control unit it attaches to the system 360 model 25 thru a disk attachment control which provides the function of the control unit disk packs are written in these attachments in ibm s count key data variable record length format the 2311 models 11 or 12 are used when attached to an integrated control of the system 360 model 20 and the disk packs are written with a fixed sector format the disk packs are not interchangeable between those written on the model 1 and those written on the models 11 or 12 the 2311 mechanism is largely identical to the 1311 but recording improvements allow higher data density the 2311 stores 7 25 megabytes on a single removable ibm 1316 disk pack the same type used on the ibm 1311 consisting of six platters that rotate as a single unit the 2311 has ten individual read write r w heads mounted on a common actuator which moves in and out hydraulically and is mechanically detented at the desired track before reading or writing occurred each recording surface has 200 tracks plus three optional tracks which can be used as alternatives in case faulty tracks are discovered average seek time is 85 ms data transfer rate is 156 kb s because the 2311 was to be used with a wide variety of computers within the 360 product line its electrical interconnection was standardized this created an opportunity for other manufacturers to sell plug compatible disk drives for use with ibm computers and an entire industry was born ibm 2314 2319 edit ibm 2314s at the university of michigan note removable disk packs and empty covers on top of the drives ibm 2314 disk access storage facility model 1 edit the ibm 2314 disk access storage facility model 1 was introduced on april 22 1965 one year after the system 360 introduction 40 it was used with the system 360 and the system 370 lines with the two channel switch feature it could interface with two 360 370 channels the 2314 disk access mechanism was similar to the 2311 but further recording improvements allowed higher data density the 2314 stored 29 176 000 characters 200 20 7294 bytes per track on a single removable ibm 2316 disk pack which was similar in design to the 1316 but was taller as a result of increasing the number of disks from six to eleven the 2316 disk pack containing the eleven 14 inch 360 mm diameter disks yielded 20 recording surfaces the drive access consisted of 20 individual r w heads mounted on a common actuator which was moved in and out hydraulically and mechanically detented at the desired track before reading or writing occurred each recording surface has 200 tracks access time was initially the same as the 2311 but later models were faster as a result of improvements made in the hydraulic actuator data transfer rate was doubled to 310 kb s the original model 1 consists nine disk drives bundled together with one price separately shipped was a storage control unit a single drive module and two four drive modules for a total of nine drives the drives are mounted in individual drawers that are unlatched and pulled out to access the disk pack because of their appearance they acquired the nickname of pizza ovens only eight drives of the nine are available to the computer at any one time the ninth drive is there for a spare for the user and can also be worked on offline by a field engineer while the other drives are in use by the customer each drive s system address is determined in part by a user swappable plug one such plug denoting a spare drive not system accessible this permits physically changing the address of a drive by changing the plug ibm 2314 a 2844 control unit can be added to the 2314 control unit which allows two s 360 channels simultaneous access to two separate disk drives in the storage facility other 2314 models came later ibm 2314 direct access storage facility a series edit in 1969 ibm unbundled the facility into separate models allowing up to nine drives eight on line attached to a 2314 storage control 2312 disk storage a one drive module 2313 disk storage a four drive module 2318 disk storage a two drive module ibm 2319 edit in a response to competition from plug compatible manufacturers of 2314 equivalent storage subsystems ibm beginning 1970 introduced a series of low priced three drive module 2319s which were manufactured by removing one module from the four drive module 2313 rebranding it as a 2319 a1 and offering it at a substantially reduced rental price this had the effect of lowering the rental price to new customers while keeping the high rental price on existing customers the 2319 a1 attaches to integrated controllers for only the system 370 models 135 and 145 conventional 2314 dasd such as the 2312 or 2318 can attach to the 2319 a1 2319 b series of three disk drives modules allow three six or nine drive attachment to a new 2314 model b storage control unit ibm 3310 edit ibm introduced the ibm 3310 direct access storage device on january 30 1979 for ibm 4331 midrange computers 41 each drive had a capacity of 64 5 mb the 3310 was a fixed block architecture device used on dos vse and vm the only s 370 operating systems that supported fba devices ibm 3330 edit 3d artist s concept of an ibm 3330 direct access storage facility shown are three 3330s and one 3333 on the right the ibm 3330 direct access storage facility code named merlin was introduced in june 1970 for use with the ibm system 370 and the ibm system 360 195 its removable disk packs hold 100 mb 404 19 13 030 bytes access time was 30 ms and data transferred at 806 kb s a major advance introduced with the 3330 was the use of error correction which makes the drives more reliable and reduced costs because small imperfections in the disk surface can be tolerated the circuitry can correct error bursts up to 11 bits long through use of fire codes the 1973 3330 model 11 features ibm 3336 11 disk packs that held up to 200 mb 808x19x13 030 bytes ibm 3333 edit the 3333 1 and the 3333 11 contain two 3330 type drives and a controller that attach to a director type storage control up to three additional 3330 type dasd six drives can then be attached to a 3333 the 3330 was withdrawn in 1983 42 ibm 3340 and 3344 edit the ibm 3340 and 3344 have similar characteristics however only a 3340 can serve as head of string there are no a model 3344 drives and a 3344 must be attached to a 3340 a model as head of string ibm 3340 edit the ibm 3340 direct access storage facility code named winchester was introduced in march 1973 for use with ibm system 370 43 three models were announced the 3340 a2 with two drives and a controller the models b2 two drives and b1 one drive b units can connect to the model a2 to a maximum of eight drives it uses removable data modules that included the head and arm assembly an access door of the data module opens or closes during a mechanical load unload process to connect the data module to the drive unlike previous disk packs and cartridges there is no cover to remove during the insertion process access time is 25 millisecond and data transfers at 885 kb s three versions of the removable ibm 3348 data module were sold one with 35 megabyte capacity another with 70 megabytes the third also has 70 megabytes of which 500 kilobytes were accessible with fixed heads for faster access the 3340 also uses error correction it was withdrawn in 1984 the 3340 was developed in san jose under the leadership of ken haughton early on the design was focused on two removable 30 megabyte modules because of this 30 30 configuration the code name winchester was selected after the famous winchester 30 30 rifle 44 subsequently the capacities were increased but the code name stuck one significant aspect of this product and the reason that disk drives in general became known as winchester technology was that this head design was very low cost and did not require the heads to be unloaded from the media winchester technology allowed the head to land and take off from the disk media as the disk spun up and down this resulted in very significant savings and a large reduction of complexity of the head and arm actuating mechanism this head design rapidly became a standard design within the disk drive manufacturing community up into the early 1990s the term winchester or winnie was used for hard disk drives in general long after the introduction of the 3340 but is no longer in common use in most parts of the world ibm 3344 edit the ibm 3344 is similar to the 3340 except that it uses fixed media rather than removable 3348 data modules each spindle has 4 logical drives each with the capacity of a 3348 70 there is no a head of string model and it is only available in dual drive models the 3344 b2f is identical to the 3344 b2 except that both drives have fixed heads over some cylinders both 3344 b2 and 3344 b2f require a 3340 a2 or 3340 a2f as head of string ibm 3350 edit the ibm 3350 direct access storage facility code named madrid was introduced in 1975 for use with ibm system 370 45 its non removable head disk assemblies hdas are sealed and included the head and arm assembly the 3350 disk geometry is 555 cylinders 30 heads and 19 069 bytes per track which give each hda a storage capacity of 317 498 850 bytes sealed hdas were standard practice on all ibm dasd hereafter disk units are identified as models a2 a2f b2 b2f c2 and c2f with each model containing two hdas the models are installed in strings of units with an a2 or a2f unit required and attached to a storage control such as the ibm 3830 model 2 or the equivalent integrated storage control of a system unit after the a2 can be up to 3 b2 units or up to 2 b2s and a c2 the c2 unit also connects to a storage control and serves as a secondary path to itself and the a2 and b2 units when using a c2 two i o operations could simultaneously take place on the string one via an a2 and a second via the c2 the valid 3350 strings are a ab abb abbb ac abc or abbc configurations the x2f as in model a2f unit is a normal x2 unit but its two hdas also have a fixed head area over the first five cylinders thereby reducing d seek time to zero for these five cylinders this fixed head area is intended to be allocated to the frequently accessed hasp or jes2 checkpoint area and thus greatly reduce head motion on the spool device the fixed head area can also be utilized for tso swap data mvt and svs and system swap data mvs wherein the swap data for svs and mvs consist of blocks of pages that have been in memory when an address space is selected for swap out those pages need not be contiguous and in general do not include pages that have not been modified since their last page in this system architecture greatly improves context switches between tso users or batch regions the ibm 3350 family was withdrawn in september 1994 ibm 3370 and 3375 edit ibm 3370 edit ibm introduced the ibm 3370 direct access storage device in january 1979 for ibm 4331 4341 and system 38 midrange computers 46 it has seven fixed 14 inch 360 mm disks and each unit has a capacity of 571 mb it was the first hdd to use thin film head technology research on that technology started at thomas j watson research center in the late 1960s 46 the 3370 was a fixed block architecture device used on dos vse and vm the only s 370 operating systems that supported fba devices ibm 3375 edit the sister unit was called the ibm 3375 and used count key data architecture which was required for os 360 and successor oses ibm 3380 edit ibm 3380 disk drive module the ibm 3380 direct access storage device was introduced in june 1980 47 it uses film head technology and has a unit capacity of 2 52 gigabytes two hard disk assemblies each with two independent actuators each accessing 630 mb within one chassis with a data transfer rate of 3 megabytes per second average access time was 16 ms purchase price at time of introduction ranged from 81 000 to 142 200 due to tribology problems encountered between he...