64Gbyte flash memory - hot stuff, unfortunately

This isn't as easy as it might at first appear.
With a decent software RAID controller, it's not too hard to persuade it that a networked remote device is just another disc onto which it should be mirroring writers.
However, the remote disc will inevitably take longer to complete those writes than the local one. So your local system becomes constrained by the speed of the link. You can queue writes locally and send them over the link as bandwidth allows, but then you don't have a current mirror any more.
These days I'd be inclined to use ZFS snapshots every (arbitrary interval), with incremental send.
Reply to
Roger Bell_West
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We could, but the sneakernet was a lot faster and more reliable.
-- mrr
Reply to
Morten Reistad
That was a rather off-topic comment for this NG: apologies. It was meant to be a specifically Tandem NonStop point. These machines were effectively a network in a box from when they first appeared in the early '70s. There were up to 16 independent processors in a cabinet, each connected to dual disk and comms controllers with mirrored disk pairs split across controllers. Individual processors weren't fault tolerant, but processes running on them were because they had a continually updated backup image on another processor and all processors continually monitored the health of each other. On top of that, up to 16 cabinets could be linked in a single network which acted as a continuation of the inter-processor commms bus in each cabinet. This meant that any processor could directly access any disk attached to any cabinet in the network.
Thats why I said what I did and enquired about network capacity, because with the Guardian OS running on Tandem hardware there was no need to periodically sync data to the disks in the disaster recovery site or even to use the AS/400 trick of sending a copy of the transaction logs to the backup site to keep the backup disks updated. The only restriction was that the linking network required sufficient capacity to handle the mirroring of writes to remote disks. This required capacity only depends on the data volume and update frequency.
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martin@   | Martin Gregorie 
gregorie. | Essex, UK 
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Reply to
Martin Gregorie
Understood. The Tandems I was involved with were CHAPS gateways, so we didn't have a disk backup issue other than mirroring: for recovery the message backup was the copy on the bank's mainframe for outbound traffic and the copy on the other gateway for inbound traffic. Either would be automatically re-sent if required as the network came back up.
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martin@   | Martin Gregorie 
gregorie. | Essex, UK 
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Reply to
Martin Gregorie
All right then: has anyone got zfsroot working on a Raspberry Pi? I think it's unlikely and probably not very useful, but it would be interesting, and it would certainly ease the backup problem that seems to be a regular topic of discussion here..
Reply to
Roger Bell_West
It might have inspired someone to go develop a fault-tolerant cluster using Pi compute modules ... :-)
Reply to
Rob Morley
Off topic?? there's a thread on the merits (or not) of metric units and electric sockets. It's easy to miss the header is "ARMv8.1?"
I'm thinking of getting it vaguely back on topic-ish as Yet Another vi v emacs debate!
--
Bah, and indeed, Humbug
Reply to
Kerr Mudd-John
AFAIK there were no patents on Unix, there were however copyright restrictions on the AT&T source code which Linux avoided by the simple (in principle) expedient of being a clean rewrite while BSD got embroiled in a legal argument over which bits they could distribute and which bits they could not.
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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
C:>WIN                                      | A better way to focus the sun 
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Reply to
Ahem A Rivet's Shot
I thought Linux was originally a clean rewrite of Minix, which was itself a clean rewrite of UNIX for early Intel chips/PCs.
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martin@   | Martin Gregorie 
gregorie. | Essex, UK 
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Reply to
Martin Gregorie
I stand corrected. Patents and copyrights are a bit of a legal nicety to me.
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A lie can travel halfway around the world while the truth is putting on  
its shoes.
Reply to
The Natural Philosopher
I am not so sure it was a rewrite of Minix.
AIUI it was a from scratch kernel that could accept Gnu Unix toolsets on top
i.e. an operating system that cane with a Unix compatible libc.
Looking at the Wiki suggests that whilst Linus did his development on Minix, it was a clean fresh brand spanking new kernel that he wrote.
And was at the time (386) hardware specific.
--
A lie can travel halfway around the world while the truth is putting on  
its shoes.
Reply to
The Natural Philosopher
There is a definite difference in the kernel structure: Minix is a microkernel architecture, but Linux has a monolithic kernel.
However, Linus used similar file system initally as Minix.
--

-TV
Reply to
Tauno Voipio
It was originally a task switcher because Linus had spotted a neat way of making one on an 80386, it grew into a complete kernel for a unix like OS. Early development took place under Minix.
Minix was not originally intended to be a rewrite of unix so much as a demonstration vehicle for Tanenbaum's book on OS design and microkernel architecture. It was however call compatible with unix from the start.
Strictly speaking Linux is the kernel, pretty much all the basic userland in a Linux distro is from GNU which was originally a project to produce an open source unix (sensibly starting with a compiler) that never produced a kernel.
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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
C:>WIN                                      | A better way to focus the sun 
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Reply to
Ahem A Rivet's Shot
They did produce a kernel - GNU Mach is on release 1.8 However as it's a microkernel there's a load more stuff necessary to make it useful, and the GNU Hurd is only on release 0.9 There's an unofficial Debian port running Hurd/Mach that I haven't tried yet ...
Reply to
Rob Morley
Which side are you on. My old editor, Codewright has had a stroke and I am finally learning a new one so I can use the same editor on the rPi and the PC. Right now I am struggling to learn Emacs as I have heard so much good about it. But it doesn't do much through the GUI. :(
Does VI even run on the PC? How well does it deal with the Unix NL vs. PC CR/LF issue? Codewright would just preserve what it saw used in the file being edited. That was *great*.
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Rick C
Reply to
rickman
From what I've heard it has so many features it could replace the entire operating system, but I like a text editor to be just that ...
I think GVim runs in most graphical environments, and plain Vim runs just about anywhere.
Reply to
Rob Morley
Sometimes politicians impose standards because it "levels the playing field" (how many times have we heard people crying out for that?) or because it protects life and limb of millions of people. I'm at least as cynical about politicians as the next man, but they do sometimes do us some good. I'm particularly grateful to the EU for mandating catalytic converters, compliance with electrical safety standards, and progressively stricter cleanliness standards for beaches, among many other things.
Let's not forget that the politicians don't (in any case that I'm aware of) create the standards; they simply mandate compliance with existing standards that various standards bodies have created.
And, yes, they sometimes make mistakes - in common with the rest of humanity.
Dave
Reply to
Dave Higton
I stand corrected.
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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
C:>WIN                                      | A better way to focus the sun 
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Reply to
Ahem A Rivet's Shot
Certainly, even the MKS toolkit for MSDOS had vi - that toolkit made MSDOS almost tolerable.
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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
C:>WIN                                      | A better way to focus the sun 
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Reply to
Ahem A Rivet's Shot
The EU didnt formulate and pass the clean air act. It always amused me how management took the credit for something that would have happened anyway just because 'it was on their watch'
--
Karl Marx said religion is the opium of the people. 
But Marxism is the crack cocaine.
Reply to
The Natural Philosopher

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