IBM System/370 145 Manual page 105

The major new characteristics; of these devices are discussed in the
following subsections.
20:10 3330-SERIES DISK STORAGE
3330 DISK STORAGE AND 3333 DISK STORAGE AND CONTROL
The 3330-series is large-capalcity, high-performance direct access
storage that consists of 3330 Di.sk storage and 3333 Disk Storage and
Control. A 3330-series string c:an consist of one to four modules (from
two to eight drives). and is cODlnected to a Model 145 selector or block
multiplexer channel via 3830 storage Control (Model 1 or 2) or via
integrated storage control conta.ined in a storage frame connected to the
Model 145
cpu.
The removable 3336 Disk Pack is used for data storage.
Track overflow, rotational posit,ion sensing, and multiple requesting are
standard features of 3830 storag'e Control and integrated storage
control. The block multiplexing' feature must be installed on the Model
145 in order to use multiple requesting and RPS.
A 3330-series string can consist of 3333 Disk Storage and Control
and/or 3330 Disk Storage modules.
A
3333 Disk Storage and Control
module consists of two independent drives and device-oriented control
functions. It must
be
the first unit in a 3330-series string attached
to a Model 145 channel via integrated storage control (ISC) or via 3830
Storage Control Model 2. The 3333 does not attach to 3830 Storage
Control Modell. The 3330 Disk Storage module consists of two drives
and does not contain the-device-oriented control functions that are part
of a 3333 module.
A
3330 module connects directly to 3830 storage
Control Model
1
and to 3333 modules. Up to three 3330 modules can be
attached to a 3333 module. Functionally, all drives operate in the same
way, regardless of whether they are part of 3333 or a 3330 module.
The 3336 Model 1 Disk Pack is used with 3330 and 3333 modules. It
has 19 recording surfaces and a maximum capacity of 100 megabytes when
full-track records are used. A 3330-series string can consist of two,
four
r
six, or 'eight drives for a maximum of 800 million bytes per
string. The removable 3336 Model 1 Disk Packs are interchangeable
across all 3330 and 3333 modules. Model 1 3336 Disk Packs are not
interchangeable with the 2316 Disk Packs used on 2314 disk drives.
(Table 20.10.2 compares disk pack characteristics.)
Each drive in a 3330 or 3333 module is mounted in a powered drawer
that is opened and closed by a slwitch on the operator's panel contained
in each module. Each panel provides the switches and indicators
associated with individual drives in the module. Included on each
operator panel are write inhibit switches, one for each drive. A switch
can be individually set to permi,t both reading and writing or reading
only on its associated drive. Wben an attempt is made to write on a
drive that is set for read opera"tions only, an interruption occurs and
IBM-supplied programming support terminates the program that attempted
to write on the protected drive. Each operator panel aiso contains a
removable logical address plug, ::;imilar to that of the 2314, for each
drive in the module. In addition, a
CE
service plug is supplied that is
to be used when IBM-supplied dia4~nostic programs are executed.
Functionally, the 3330-series provides more capabilities than the
2314, particularly in the areas of performance and availability. The
3330-series supports all the standard 2314 commands (except the file
scan commands) in addition to
se~iTeral
new operations, including RPS and
error recovery commands. (Table 20.10.3, at the end of this subsection,
compares 3330-series and 2314 features.) The 3330-series also is an
attractive growth device for the 2321 Data Cell Drive.
A Guide to the IBM System/370 Model 145 95