Pi lightweight server with USB SSD instead of powered HDD?

On which ICL hardware and OS?
Not, presumably a 1900 capable of running George 3, since that had one of the best backup systems I've ever seen. George automatically extended its file system onto tape, by making backups at predefined intervals onto 1 to 3 tapes in parallel. If the on-disk part of the filing system got over full, the largest, oldest backed up files were erased from the disk store until the free space quota was reached. When a logged-on user or batch job needed any of these files, George 3 asked the operator to load a tape containing the most recent copy(s) of the file(s) and put them back on disk. It also had the ability to free old backup tapes by moving any files that hadn't been deleted and had no more recent backups back to disk and then removing that tape (and its parallel copies) from the active backup tapes list.
VME/B, the 2900 OS did something recognisably similar, though with tweaks to deal with large databases - IIRC these could be duplicated onto removable disks rather than tape.
True enough, but a well-designed security system should not interfere with normal activity by an authorised user. UNIX/Linux is less annoying than other OSen I've used, but it limited by being a two-level system ('root' + other users).
I think George 3 was better here, since it had a user hierarchy. Under it :manager was the equivalent of 'root' and also owned the whole filing system. It could create other users and give them storage and CPU budgets. These in turn could create subordinate users and give parts of their budgets to them.
FWIW, Multics (1967) was the first OS with a hierarchic filing system.
George 3 (1969) seems to be the first widely used OS to support a hierarchical filing system (I think there must have been more 1900s running George 3 than the 80 Multics installations: I've used or been sysadmin on 6, but I have no idea how many G3 installations there were overall.
UNIX doesn't seem to have left Bell Labs until it was rewritten in C (1973), but wasn't really portable before 1978.
Microware OS9 was released 1980, so precedes MS-DOS (1981) by a year. Linux was first released in 1991.
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Martin    | martin at 
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Martin Gregorie
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Well I did the research and it seems that what makes the difference is the use of a LAN9514 chip which contains all the Ethernet and 4 x USB circuitry, and carries power limiting circuitry too.
A definite example of creeping featurism...
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Reply to
The Natural Philosopher
On some models - those with ethernet - it appears that they use a chip (LAN2514) which takes it upon itself to monitor and limit power. Obviously its intended for kit that has limited internal power supplies, but it becomes pointless if you have an external one.
Why they don't bypass its power stuff and feed power straight to the USBs, only some pointy headed Pi designer knows.
I am frankly flabbergasted that such a crap piece of design was incorporated
As an electronic designer I simply didn't believe they could be that stupid.
Apologies to all I offended by doubting them.
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Reply to
The Natural Philosopher
DRS3000 (Intel) and DRS6000 (SPARC) running Unix. This was in the 1990s. The source code that we bought was written for Intel, and we had to do a *lot* of #ifdefs for SPARC to reverse the byte ordering of multi-byte integers between the format in the packets received and the native format of the CPU.
Reply to
NY
Would be unusual to mean bit in that context. I can believe a 1984 Z80 based computer to have 64 KiB! They also write "12 Kg" so I don't trust their capitalisation skills.
Reply to
A. Dumas
Interesting: that was after my time on ICL kit. The really odd one for me was 18 months in NYC (1976/77) building an sales and accounting system for a toy manufacturer on a 2903. At that time, although the 2903 was always capable of handling multiple 24x80 green screen terminals, there was no system or skeleton for managing a set of screens accessing a common set of indexed access files, so I designed and built one. Somewhat to my surprise it ran successfully the first time we tried it. FWIW this skeleton was written in PLAN, with the file handler and application code in COBOL. Officially, there was no PLAN assembler on the 2903, so we took a disk to the only 1900 installation in NYC and copied the PLAN3 software and libraries. It was sometimes useful to be hired by ICL!
The last major project I did on ICL kit was at the BBC, building ORPHEUS, the original Radio Three music planning system. That was on a dual 2966 installation, so much bigger than the ex-Tarmac 2966 at NMOC. The project started in 1980, went live in 1982. It was written in COBOL using an IDMSX database.
My last contact with anything connected with ICL was around 1986. By that time I was at Logica - easily the best place I ever worked.
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Martin    | martin at 
Gregorie  | gregorie dot org
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Martin Gregorie
Wouldn't that require much wider power rails? Maybe there simply wasn't enough space on the PCB to accommodate that without making the PCB bigger?
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Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
That might be the case for your Pi, but UNIX/Linux filing system permissions are a lot more flexible than that.
---druck
Reply to
druck
These are all multilayer boards
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Reply to
The Natural Philosopher
It was not unusual in some 8 bit micros to have paged RAM and ROM. It made stuff pretty tricky to program tho
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Truth welcomes investigation because truth knows investigation will lead  
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Reply to
The Natural Philosopher
It's not a crap design, it's deliberate to prevent to prevent damage to both the Pi, who's circuit board is not designed to take high current, and the power supply, which may be some cheap one which may overheat when trying to supply too much current.
If you want large currents use a powered hub, rather than trying to turn the Pi in to a toaster.
---druck
Reply to
druck
By 1984 paged memory was common on Z80 systems 256K DRAM chips were getting cheap so 256KiB was an easy option, with a little care you could build the board to take either size chip.
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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
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Reply to
Ahem A Rivet's Shot
Understood, but are the ground and positive rails duplicated on more than one layer? Or are they significantly wider than signal lines? Its difficult to tell from visual inspection.
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Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
On Sun, 18 Jul 2021 08:28:38 +0100, The Natural Philosopher declaimed the following:
Partly because the USB spec itself says devices must start in the 100mA mode and negotiate with the host if they want the 500mA load.
formatting link
""" The limit to device power draw is stated in terms of a unit load which is 100 mA, or 150 mA for SuperSpeed devices. Low-power devices may draw at most 1 unit load, and all devices must act as low-power devices before they are configured. A high-powered device must be configured, after which it may draw up to 5 unit loads (500 mA), or 6 unit loads (900 mA) for SuperSpeed devices, as specified in its configuration (i.e. because the maximum power may not be available).[42][43][44][45] """
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	Wulfraed                 Dennis Lee Bieber         AF6VN 
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Reply to
Dennis Lee Bieber
Typically a digital board will have entire layers dedicated to + and ground, but there may not be high-current access to them, only small vias. It's a matter of minimising coupling through the rails rather than supplying lots of current.
I think this issue has been settled by quoting the USB spec. In any case, a Pi isn't a power supply, and any significant current required by a peripheral should be fed directly to it. Using a Pi as a power supply will make it run hotter, an important consideration for a Pi4.
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Joe
Reply to
Joe
The tendency used to be to have ground on top solid as a shield, and another layer was the power supply lines.
But I never designed a surface mount board :-)
signal wiring could then go north south in one layer and east west on another!
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In a Time of Universal Deceit, Telling the Truth Is a Revolutionary Act. 

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Reply to
The Natural Philosopher
Nice!
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Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Maybe I've been lucky, YMMV, etc, but I've had an RPi 3B+ with a WD Elements portable hard drive (no separate power supply) working for several years without any problems that I've noticed.
John
Reply to
John Aldridge
Yes, me too with a Seagate Expansion Portable (2.5" usb powered hdd) before I replaced it with a Pi 4 with ssd. Was my home web server etc. for years, never crashed.
Reply to
A. Dumas
I've only ever done two layers, where that strategy was good for minimising vias.
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Joe
Reply to
Joe

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