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One-Machine Linux Cluster
An AC wrote: Forget Beowulf ? clusters, Jacques Gelinas has made available a kernel patch to enable many virtual servers running on the same machine, even the same kernel. Read his original message posted to the Linux kernel list." Imagine what this will mean for hosting companies...
haha.. better read the fine print and make sure you actuallu get your own *computer* including box and powersuppy, and motherboard-- or you may end up sharing your box with 100 other ppl :-P
Slashdotted before I could read the whole thing. :( But, as a sysadmin for a smallish web devolopment/hosting company I could REALLY use some separation between certain clients. Sure, this isn't ready for production systems but one day it may be.
The patcher is right...modern CPUs (for my industry) have PLENTY of power. What I hate is having to run some third party app for a client (even in a Linux environment) that *might* affect the whole machine. This patch holds the promise that I won't have as much to worry about.
Yes, this is a good thing.
Here before all but 8486 of you.
Well hey, on a multiprocessor machine it might be interesting. Dedicate a processor for each node and you have four beowulf nodes in one box.
Not only would it be cool for developers to test Beowulf-enabled code, but it would be awesome to have each node independantly accessible from the network.
Basically the same idea as Galaxy. Check it out for ideas.... http://www.openvms.compaq.com/availability/galaxy. html
This has just about zero to do with clustering, if anything this is the opposite of clustering. However this IS very very interesting for Web Hosts and just about anyone else that wants to create and maintain multiple environments for developement, test, etc. Image, being able to carve up a mid-range machine like you can an S390 (or other Mainframe class machine Like Sun's E10/15K). So suppose IBM takes this an runs with it. Linux is already ported to RS/6000 and AS/400, now you could get 8 processors of RS/6000 goodness, run production on 4 processors, Test on 2 processors, and Dev on 2 processors.
The devil will be in how you refresh test and dev from production, but that can probably be done inside Logical Volume Manager.
This is very very cool stuff it will be very ineresting to see how it stacks up against the big boys in Virtual machine space.
What if it is just turtles all the way down?
... of clustering. Its... slicing your box up...
Can anyone tell me how this is different than User Mode Linux?
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Someone doesnt understand the reason for a cluster
/. article to hosting companies. This is like the Sandinavian ISP that replaced a bunch of Sun boxen with a much smaller number of larger IBM mainframes. The mainframes run IBM's VM (stands for Virtual Machine), which is roughly analogous to the "root-kernel" dicussed in the linked-to articles, then runs many independent copies of Linux under VM. Each user gets his own copy of Linux to screwup^H^H^H^H^H^H^H do as wishes with. VM 'fools' the copies of Linux into thinking they each have their own machine. Here we have Linux replacing VM, so now a Free product can do some of this (assuming it works, which, being brand new, I wouldn't bet my income on. But I'll bet it will work well soon.), though not all: VM lets you run multiple OS's on the box, which this doesn't. But it does a lot - separate root logins/passwords and process lists for the 'vurtual Linuxen', for example.
I think that was whoever wrote the headline. This doesn't buy you what a cluster buys you, which is more MIPS and RAM working on the same problem. This buys you multiple relatively independent environments on one machine. Hence the reference in the
"that's not encryption - it's a new perl script that I'm working on..." - from some Matrix parody
Hostpro, now Interland has this sort of thing for freeBSD. It used to be called vserver. The new improved version is called Freedom. It's been out for years.
I wonder how this would work with mosix... it could be a dream system!
You could use mosix to combine the compute resources of several boxes to look like one box. And then, you could use this divy up the space so that people don't step on each other. When anyone (working in thier own space) kicks off a large compile, the load would transparently be distributed among all the boxen.
Of course, I have zippy experience with any of this, but it sounds possible.
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Jail isn't the same as this. If you read the jail manpages, it gives lots of examples how running with a jail involves very interesting problems for some uses. This different technique has different problems for other uses, and does some things nicely that jail does not. And user mode Linux is different, and better for yet other purposes.
(Goodbye, karma.)
I know this is completely off-topic, but here it is anyway.
Your understanding of the prefix "meta-" is incomplete. In addition to indicating syntactic self-reference (see Hofstader), it can also indicate semantic self-reference (see... well, Hofstader; he talks about this, too, in his discussion of GOD: God Over Djinn).
SGI has a device for connecting crossbar routers together to form large single-system-image computers. It's called a metarouter:a router for routers.
Likewise, a cluster of clusters would be properly called a metacluster. Since "Beowulf" is commonly synonymous with "cluster," the term "meta-beowulf" is pretty much correct, even though it makes me cringe.
Linux can natively be configured to enforce disk quotas and (with more difficulty) manage network bandwidth without any special virtual server software. Also the native unix process scheduling algorithm does reduce the priority of CPU bound tasks. The getrlimit(2) system call can be used to set various limits per process (not per virtual server unless the virtual server runs as one process I guess.) I know of no way to specifically limit disk bandwidth on Linux.
Freeware such as s_context and user mode linux provide no control over how much resources one virtual server gets over another besides disk usage. Other limited resources like CPU, disk and network bandwidth (RAM?) are shared just like they would be shared by separate processes under a single Linux system.
FreeVSD is not a virtual server, but a collection of scripts, binaries and multiple copies of hard-linked read-only filesystems for the common system environment. It is has the best chance for winning the total performance award but has no extra features for resource limits between systems.
True virtual machines. (E.g., vmware) provide very good isolation, but this leads to little sharing of excess unused resources between virtual servers I believe. They also have poorer performance in general because so much emulation is done.
The commercial, proprietary Private Server product from Ensim seems good from the marketing blurbs which say that they have "their own guaranteed share of the servers resources, including CPU, memory and bandwidth". I wonder what the performance penalty for this is and how much does it cost? Can anyone comment?
It's the control over it.
Mainframes have insane amounts of control over user processes (a Linux image essentially becomes same), as well as the ability to allocate more resources, fewer, provide fine-grained process accounting, shut down processes, migrate them elsewhere (part of the IBM dataceter Linux concept is the ability to migrate nodes around the country as needed).
What a mainframe doesn't have to offfer is insane amounts of processor power or memory. Disk, and disk I/O are quite another matter -- the amount of aggregate bandwidth a z390 has to offer is impressive.
PC-based virtualization clearly has some advantages, through not all of those offered by a mainframe. A rack of virtualized PCs probably does offer a higher processor density than the equivalent mainframe, however.
What part of "gestalt" don't you understand?
Much respect to this guy. He's taken something thats big, hairy and complex and looked at it from a different direction. Because he's got access to the source he's been able to do something novel with it in what appears to be an efficient and simple way...you couldn't do that with any of the closed source OSes out there today!
/bin /lib etc. from a generic set but users can modify them if they need to - this would allow a sysadmin to keep the default system current while not preventing 'owners' of an individual image from being able to change things if they need to....I vaguely remember something like this for CDs - anyone got the details? Time for a bit of experimentation ;-)
The beauty of this is that there's *one* kernel running so, apart from any overhead of selecting the environment, you pretty much get the same performance as running native. This has got to have 1001 applications.
One of the things I'd personally like to see is some kind of overlaid filesystem so each image by default gets
I wonder if it would be practical to associate absolute CPU time limits or CPU usage percentages with a security context id in order to prevent a certain security context from hogging all CPU ressources.
A similar thing would be desireable for resident set size (real RAM usage) and virtual size (process size) per security context.
Yes, the patch doesn't support hardware dedication. But my SUN background makes me ponder a line of thought.
:)
In Solaris, there are the psr* family of commands for processor administration. psradmin -f 0 will turn off processor 0. As long as this isn't physical powering down of processors, and simply instructions to the scheduler to disregard p0, you could, on the above vm, do something like:
Prod: psradm -f 4,5,6,7
Test: psradm -f 0,1,2,3,6,7
Dev: psradm -f 0,1,2,3,4,5
Leaving procs 0-3 for Prod, 4-5 for Test, and 6-7 for Dev.
Along the same lines, at boot time you can explicitly state memory ranges to the kernel, if linux can't detect your memory right, or you have known bad memory you want to avoid. With the same thought, the Prod, Test, and Dev kernels can be brought up explicitly stating the 0-2G, 2-3G, and 3-4G ranges as usable memory addresses.
You run into more problems when it comes to peripherals in the box, but how many serial ports do you really need? Just specify ttyS0 in the VM with the addresses of ttyS0,1,2 of the physical server.
Am I smoking crack, or should I just stick with my much-more-hardware-flexible Sparc architecture
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