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#21
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What are the practical (or real) advantages of Intel VT and TxTtechnology (Q8200 vs Q9300) ?
Robert Myers wrote:
I had a really hard time visualizing a VM until I actually used one. Now things are much more clear, and, while I still don't understand the virtue of running 100 Linux servers on a mainframe, I can see some definite advantages for me: I can run Linux as a guest on Windows and have access to both environments at the same time. I'm assuming that it's the VT-x technology that allows me to run the virtual Linux box with it's own IP address. My router sees two distinct computers, in spite of the fact that I have but one ethernet card. I can ssh into the guest Linux box from the host box and use sftp to move files back and forth between the two machines. The virtualized network interfaces actually predates the virtualized processor environments by many years, and it's not really achieved through the virtual processor mechanisms, nor is processor virtualization necessary. It's simply a matter of changing the MAC ID of the packets. Usually the MAC ID is whatever is built into the firmware of the network adapter, or sometimes even into the BIOS firmware of the host machine. But this identifier is interceptable and changeable. Prior to processor virtualization, I used to run Sun machines with multiple websites, each website was assigned its own virtual network interface and was thus easily routable by MAC ID alone. Yousuf Khan |
#22
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What are the practical (or real) advantages of Intel VT and TxTtechnology (Q8200 vs Q9300) ?
On Aug 7, 5:13*pm, Yousuf Khan wrote:
The virtualized network interfaces actually predates the virtualized processor environments by many years, and it's not really achieved through the virtual processor mechanisms, nor is processor virtualization necessary. It's simply a matter of changing the MAC ID of the packets. Usually the MAC ID is whatever is built into the firmware of the network adapter, or sometimes even into the BIOS firmware of the host machine. But this identifier is interceptable and changeable. Prior to processor virtualization, I used to run Sun machines with multiple websites, each website was assigned its own virtual network interface and was thus easily routable by MAC ID alone. I mentioned it mostly because the machine can talk to itself without the intervention of a third party. For me, it's very convenient because I don't have to worry so much about which environment something is in. Mostly, I was always aware of the privileged instruction issue and, no matter whether it could be gotten around or not without VT-x, it always sounded like it had to be baling wire and chewing gum, and I had no interest in experimenting. That is to say, whether it's supposed to work or not, I wouldn't bother with virtualization without explicit hardware support for it because of the issues with virtualization and x86. Good for vmware that they could work around it; it wasn't worth any kind of risk for me. Now that it's well- supported and can be had for free, it's pretty nifty. Robert. |
#24
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What are the practical (or real) advantages of Intel VT and TxT
On Aug 8, 9:53*am, wrote:
In article , (Robert Myers) wrote: ... while I still don't understand the virtue of running 100 Linux servers on a mainframe One of the major advantages, from the PoV of IBM, and of the people in their customers who have built their careers round mainframes, is that it provides a new reason for having a mainframe. It can also take up less space and consume less power, and so on, but that depends on how hard your "Linux machines" are being worked, and what the other pressures on the organisation are. It seems as if, by virtualizing Linux, you are giving up one of the few genuine advantages of mainframes: they are usually not an attractive target for hacking. If you virtualize Linux on them, the only advantage you have left is that it's not x86, which advantage you can get from other platforms (even and perhaps most compellingly Itanium) at a much lower price. Mainframes like to stay busy (translation: if your mainframes aren't busy, you're burning big money), and aggregating lots of servers is one plausible way of keeping any computer running servers, which spend much of their time waiting, busy. I assume that the sales folks at IBM have the pricing worked out (the same hardware is much cheaper if it runs Linux) so they can make the case with a straight face, but Itanium running HP-UX still sounds pretty attractive by comparison. Not my side of the universe, anyway. For people running lots of servers, the need for virtualization is obvious and hardware support on x86 is a no-brainer if you're not trying to protect Itanium, as Intel no longer is. For the rest of us, it looks like a neat way to build sandboxes very cleanly. As an example, my employers have a whole lot of PCs, running Windows or Linux, running overnight each night testing the day's changes to CPU-bound software. We use the developer's desktops for this overnight, as well as lots of other machines. Notably, when a developer's desktop finishes its three-year depreciation life, it goes into the test farm, and does another 2-4 years there, depending on how fast it goes obsolete or breaks down. Some corporate IT management types have been trying to convince us to buy blade servers for the test farm. They claim it will save money, but we can't see how and they can't demonstrate it. We have enough space for the old machines. While we could cram the same CPU power into less space with blade servers, *we have no other use for the space unless we are allowed to hire some more people. Blade servers, like mainframes, are a more expensive way of getting the same CPU power than ordinary desktops bought on a bulk purchase deal. Nothing about blade servers makes sense to me except that they are cute and are more readily adapted for telcos. I have yet to see the TCO argument about older PC's settled definitively. Most calculations I've seen indicated, a few years ago at least, that computers aged out of being cost effective for compute- intensive operations after about three years. After that, you were better off buying new than continuing to pay for electricity to run obsolete equipment. Where the break-point is depends on the cost of electricity, obviously. It also depends on the time derivatives of watts/flop, of new-hardware-$/flop and of the cost of electricity. From the POV of a departmental budget, though, maybe you don't care about the cost of electricity. Robert. |
#25
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What are the practical (or real) advantages of Intel VT and TxT
In article
, (Robert Myers) wrote: From the POV of a departmental budget, though, maybe you don't care about the cost of electricity. Yup: it's a site overhead, rather than a departmental thing. Maybe it should be departmental, but getting the finance people to organise things so that we can make the trade-offs at budgeting time could be hard. When you testing isn't one huge pool, but lots of separate things, such as several different customers' apps being run with new versions of the libraries we produce, using the customers' test sets, using separate machines for each test set can be a hell of a lot easier to organise. Our usage of additional CPU cores is also rather less than perfectly efficient, which tends to reduce the CPU/watt advantages of newer machines. -- John Dallman "C++ - the FORTRAN of the early 21st century." |
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