isham research
An interesting side-effect of the new I/O channel support in FLEX-ES Release 7 is that conventional mainframes can now access a FLEX-ES system's real and emulated peripherals. The applications that immediately come to mind are sharing the FLEX-ES system's emulated mainframe DASD from a "real" mainframe and exploiting FLEX-ES's highly popular FakeTape (tape file storage on mirrored Linux disks) from a real mainframe.
But one option is not to run an IBM operating system on the FLEX-ES system at all.
FLEX-ES emulates a vast range of IBM mainframe peripherals - not only the current stuff, but everything back to the dawn of time. IBM 1403 printers, 2314 DASD, FBA DASD, 3420 tapes, etc., and everything since then are supported in emulation. Accessing these peripherals does not require an IBM operating system in the FLEX-ES system - such a system is called a CU Behaviour Server.
The big differentiator to other systems (such as those supplied by Bustech, EMC, HDS, Luminex, etc.) is that a CU Behaviour Server is neither single purpose nor limited to its initial functionality. Peripherals of different classes and types can be added or deleted at will by the Business Partner or sometimes even the user, giving unprecedented flexibility - ideal for the small to medium user.
And - since there is no IBM software license to worry about - the underlying xSeries platform can be swapped for a higher performance model at any time and at standard market prices.
Programmes that are dependent on specific hardware devices - not physically attachable to current IBM mainframes - can now have those hardware requirements (usually specific printer or DASD types) met by a CU Behaviour Server. So such "stranded" applications can be moved to a more modern IBM mainframe server.
Users with tape applications on real mainframes would be foolish not to review the FLEX-ES FakeTape feature. Traffic on the open FLEX-ES mailing list suggests pervasive use of the feature and a considerable user-contributed code base to automate tape operations very economically has aleady been built. It is also possible to use SCSI cartridge tape drives as if they were mainframe drives, and to read and write the AWS tape format.
As a pure DASD subsystem, the CU Behaviour Server has some extremely interesting characteristics. For full-bore online use, it will probably not perform at the levels of top-of-the-range dedicated purpose-built storage systems - though it may give the lower-end systems more than a run for their money. There are also attachment and cache size limitations. But it does represent a gateway to commodity disk prices - if Linux on Intel supports it, so does the CU Behaviour Server. Subject to the ESCON attachment and performance constraints, extra space could be added to an emulated 3390 subsystem using disks bought by mail order or on the way home from the office. As soon as disks with higher rpm or capacity are available, in they go - with no need to wait for a manufacturer to adopt them, announce them and dream up a ludicrous upgrade fee.
Another thing FLEX-ES is very good at is communications - both using its own facilities and those of the underlying Linux base. If Linux on Intel can talk to it, so can a mainframe attached via a CU Behaviour Server. This could include local 3270s via TN3270 clients, 3172/XCA Ethernet or Token Ring, or pretty much anything supported by Linux.
One 3270 application, of course, is system consoles. This naturally raises the question of availability - consoles are critical devices and large mainframe systems have stringent availability requirements. The CU Behaviour Server uses standard IBM xSeries servers - servers that now run hundreds of thousands of businesses all over the world. The FLEX-ES mailing list anecdotally suggests that FLEX-ES availability on IBM xSeries servers meets or exceeds the availability of individual users' experience of real mainframes, although it must be remembered that most users have migrated from fairly old hardware. Nevertheless - looking forward - which is likely to provide better availability in the future: a special purpose device manufactured in the hundreds or thousands, or one manufactured to sell against fierce competition in the hundreds of thousands?
Maintenance costs for the peripheral farm are a major factor in the viability of low-end mainframe systems. The FLEX-ES CU Behaviour extends the benefits of device emulation - especially the cost reduction - to those who choose to remain on "real" mainframe hardware, and also permits the relocation of device-dependent applications to modern mainframe hardware. As such, it greatly improves the viability of small to medium mainframe systems.