IBM hopes that system-managed storage, compression technology will give 3495 the edge
The most photogenic but certainly not the star of the announcements is how IBM UK very rightly introduced its 3495 Tape Library Dataserver. IBM’s belated attempt to dislodge Storage Technology Corp is said to be an in-house development, although the robot comes from General Motors Corp and the design is similar to the 3850 library that IBM introduced in the early 1970s and dumped in 1987. So was the 3495 worth waiting for? It measures a staggering 92 feet in maximum configuration, 44 feet minimum, and the robot runs along rails installed in the bottom of the enclosure. Just how many users are prepared to rearrange their computer suites to accomodate it remains to be seen. It may apocryphal, but some cynics say that a German beta-user was refused a safety certificate because the beast is such an obstacle that it broke local fire regulations. Size aside, if that’s feasible, the four models hold between 6,500 and 18,500 cartridges, and handle 18-track and 36-track tape. The tape management software is fairly advanced, but it seems unlikely that that will be enough to persuade StorageTek users to defect to the IBM camp. What might swing them is 36-track capability and software compatibility – only IBM devices can implement System-Managed Storage. It’s a scare tactic used fairly successfully by the IBM-compatible Comparex Informationssysstemme GmbH with its automated tape library, the 6388. The 3495 automates and manages the retrieval, mount-demount, and storage of tape cartridges. It is available as the L20, L30, L40 and L50 with a cartridge capacity of 5,660 to 18,920 cartridges and from four to 64 3490 tape transports. It is managed by DFSMS/MVS in an MVS environment with VM/ESA support intended at some point and planned AIX/ESA attachability. With Escon channels, attached 3490s and the 3495 can be located up to 14 miles from a processor. The 3490 Library Attachment Facility connects the 3490 Magnetic Tape Subsystem to the Tape Library Dataserver. Within the 3495 Tape Library Dataserver, a cartridge accessor moves tape cartridges to and from tape drives, storage racks within the tape library, and input-output stations. The cartridge accessor is controlled by host system commands and licensed internal code residing in the 3495. The manager determines if the mount request is for a scratch mount, and if it is, the Integrated Cartridge Loader is indexed. The library manager licensed internal code determines the physical location of the requested volume and directs the cartridge accessor to the storage rack and storage cell location containing the volume. The accessor retrieves the requested tape from its storage cell by moving to the specified cell and mounts it onto the specified tape drive. IBM says that the 3495 in conjunction with 3490s can achieve a peak-hour throughput of more than 200 mount-demount cycles per hour by using 3490 Integrated Cartridge Loaders.
Systems Management software
The 3495 Tape Library Dataserver with the DFSMS/MVS software uses the Tape Mount Management methodology, so that small data sets can be allocated to the appropriate media by using ACS, Automatic Class Selection, routines of DFSMS/MVS, resulting in small data sets being placed on a fully-expolited cartridge. This is said to provides improved response time for end users at less cost, without changes to Job Control Language or any involvement by the end user. AT&T Co’s AT&T Paradyne, in conjunction with IBM, is developing a remote channel extender. This is intended to enable the 3495 to be located at a distance beyond the capabilities of Escon over wide-band T3 telecommunication links.
Availability and Pricing
Production testing of the Dataserver began in the second quarter and the Early Support Programme will begin in the fourth quarter with general availability in the first quarter 1993. The 3495 models L20, L30, L40 and L50 cost $395,000, $605,000, $705,000 and $851,000 respectively. The Library Attachment is either $2,500 or $5,000, and monthly
maintenance costs are from $3,150 to $7,670. – Janice McGinn
Biggest model has theoretical storage capacity of 15.4Tb
The 3495 Model L20 has an actual capacity of 5,660 to 6,440 cartridges, allowing for a theoretical capacity of 13,584Gb to 15,456Gb of data, and a maximum data density of 33Gb to 42Gb per square foot. One 3490 A-unit and up to four 3490 B04/B40 units will attach to this model. Model L30 has an actual capacity of 8,480 to 10,600 cartridges, a theoretical capacity of 20,352Gb to 25,440Gb and a maximum data density of 35Gb to 57Gb per square foot. Up to two 3490 A-units and up to eight 3490 B04/B40 units can attach. The 3495 Model L40 has an actual capacity of 11,300 to 14,760 cartridges, a theoretical capacity of 27,120Gb to 35,424Gb and maximum data density of 36Gb to 66Gb per square foot. Up to three 3490 A-units and up to 12 3490 B04/B40 units can be attached. The L50 comes with an actual capacity of 14,120 to 18,920 cartridges. a theoretical capacity of 33,888Gb to 45,498Gb and a maximum data density of 37Gb to 73Gb per square foot. Up to four 3490 A-units and up to 16 3490 B04/B40 units can be attached. It is important to remember that the maximum cartridge storage capacity decreases as additional 3490 control units and tape units are added, and that the IBM-quoted capacity assumes using a 3490 Magnetic Enhanced Capability Tape Subsystem, IDRC with a three-to-one 1 compaction ratio. Also assumed is that the Enhanced Capacity Cartridge System Tape and all cartridges are filled to capacity, but of user variations, this capacity may not be achieved. Access time performance can vary depending on user workload, data set characteristics, and the ratio of cartridges to drives, and while IBM talks of a 30 second access time, that may not be achievable. In addition, the 30 second access time suggests that IBM sees the 3495 as a write-only system, although it does have read capabilities. Finally, density is dependent on the number of drives installed, and data density decreases as additional drives are added to the configuration.
