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An Overview of Virtualization Technologies
PCM2 writes "Virtualization is all the rage these days. All the major Linux players are getting into the game with support for Xen, while Sun has Solaris Containers, Microsoft has Virtual PC, and VMware arguably leads the whole market with its high end tools. Even AMD and Intel are jumping onto the bandwagon. InfoWorld is running a special report on virtualization that gives an overview of all these options and more. Is it just a trend, or will server virtualization be the way to go in the near future?"
Virtualization is one of the best things since sliced bread and I believe it's here to stay. First of all, it spells an end to multi-booting. I have erased my secondary OSs and I run them in VMs under my main system. A performance hit does definitely occur by I am willing to pay such price for the greater ease of use. Secondly, just think of the possibility to move server images from a physical server to another one, literally freezing it here and awakening it over there - InstaScaleOut(tm) must be a server admin's wet dream.
Of course, as with all abstraction layers, it introduces complexity and takes a toll in the form of performance - but we all know absraction layers have been increasing all the time since the beginning of time.
Global warming is a cube.
We run 2x VM Ware ESX Servers on Sun x4200 servers (w. 8 gig o' ram :) - the web-gui for ESX is second to none, incredibly easy to configure virtual machines. It's got us seriously considering moving more than just our dev enviroments over to virtualised hardware.
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Now guess who said that, and when. :-)
Robert P. Goldberg said that, in 1974.
The fun thing about this is, it's still a very accurate statement. Other than in 1974, though, it doesn't solely apply to mainframes, but, as someone wrote in an earlier post, to everyday computers: desktop systems. I think that's great, and the above quote is more true than ever. Working on Mac OS X and having a Parallels session up and running where some Java application (for example) is tested in a Windows or what environment... lovely.
Yes, I'm a virtualisation enthusiast, if you haven't guessed so already. ;-)
I read the article about Xen, because Xen is what interests me. I'll go back and read the others later. Looks like more of a slashvertisement than anything useful, esp on the Xen writeup.
.. but I am asking the author .. Please don't make something very amazing like Xen disappoint people because you're publishing information you really have not researched that is not accurate.
;)
From TFA:
>> Use the "dd" command to copy the boot drive from another server to a local file, point Xen at that file, and boot
>> the VM (virtual machine). Who needs consultants?
Apparently, the author does, and they have not been reading the Xen devel or user's mailing lists.
File backed virtual block devices can be very problematic for high volume services and applications such as MySQL, Apache and others. Most of us really using Xen on deployments that 'matter' have switched to SANS and using either LVM or real partitions.
Think about how long it takes to create a 3 GB loop device, then copy over the contents over a 10 or 100 meg switch (as you'd find on a hobbyist's desktop).
Migration only takes a few seconds once that's done
If you want to write information on hot topics to draw readers and slashvertise it, great - go for it. Just be sure its accurate.
They also barely touched on what is so magic about running 32 bit guest kernels inside of a 64 bit host, the new Xen credit scheduler, and other really cool things going on with Xen.
If you're going to present yourself as an authority, please present fact, and all of the facts. Please don't setup something like Xen (which many people are working very , very hard on, HP, IBM, Novell, Redhat to name a few) to just dissapoint new users. Nobody would say "Wow that article must have been wrong", they'll say "Wow, Xen is too hard to get working like that article said". Be careful what you capitalize on to sell a few ad clicks
Do I misunderstand, or is there are real advantage on running product X in one VM and product Y in another (or even second instance of product X). What is the advantage of that scenario over simply running X and Y (or two X) on the same box.
Well for one, it makes separating X and Y onto different boxes a year down the road pretty well effortless. (whether its for load balancing, hardware upgrades, or whatever)
For another it makes upgrading X possible without having to worry about an impact on Y. Doubly handly in "validated" environments (e.g. FDA regulated)
For another it gives another tool to manage security, as its trivial to partition users and applications.
Not to mention the ability to mix OSes at will (including different versions of the same OS). X has been certified on Debian but not RHEL? Y has been certified on RHEL but not debian? Run that X on debian, Y on RHEL, oh and run Z on Windows 2003, all on one physical box. Very convenient if you need to run 3 low load apps but on different OSes.
I was with you until the "array of blade servers" part. Blade servers are acceptable IF you are short on space. They are less than ideal and more expensive than traditional servers for most other situations.
I have been lurking some VM forums and the consensus seems to be to avoid blades whenever possible.
Keep the Classic Slashdot.
System architecture is changing in a profound way that will somewhat limit the commoditization on which virtualization depends. It's not just a matter any more of CPUs doing calculation and ordering up random disk accesses. RAM speeds, memory bus speeds, interprocessor pipeline speeds -- that stuff all matters a lot now. This is most evident in data warehousing/analytics, where data warehouse appliances (Netezza, DATallegro) and even memory-centric technologies (SAP, Applix) are becoming more important, but it could also be a broader trend.
I've written about some of the details at http://www.dbms2.com/
No way do I dispute the benefits of virtualization in OLTP, messaging, and so on. It's just not the be all and end all.
To err is human. To forgive is good system design.
In theory yes, but just like the shared hosting deals about offering the likes of 20GB of storage, a terabyte of bandwidth and a plethora of features all for $7 a month (yes, Dreamhost) you would have to convince the customer they're better off spending their pittance on a 'smaller' package (a virtual server instead of a dedi). How do you convince somebody that going with a virtual server is worthwhile when more generous shared hosting and quite low dedicated server prices are pushing from both sides?
At the moment virtualised 'mini servers' seem to still be mostly targeting people wanting to step-up from shared 'prey the resources are there when you want them' hosting, not those with a dedi's looking for better value for their money. Some providers try to push virtual servers onto customers who have outgrown their shared hosting account, but I doubt you'd find those same providers approaching their dedicated server customers and saying "Hey, you're really not using the resources you have, you could save some cash by downscaling to a virtual server. Interested?"
On top of this,I would wager squeezing hundreds of customers onto a shared server for $7/month still beats sticking 4-32 virtualised customers on a single server in terms profitability (Yes, sure, you have to deal with the top few percentile who are outgrowing the system to keep everyone happy).
This is just my viewpoint from a consumer, but it seems to me the gap between shared and dedicated hosting is somewhat awkward to sell.
One of my company's clients used VMWare to virtualize the server software we provide them. A few months back they had a massive power outage that caused them to lose large portions of their primary data center.
They weren't running one of our replicated setups, so we were expecting to spend the next week rebuilding the server and configuring our software.
Instead, they grabbed the most recent backup of the VMWare image and booted it up on a completely different server over 100 miles away.
End result?
About a day's lost data and an hour of down time. (The backup was already at the remote site)
I've been pushing for VMWare usage in our test environment to reduce our hardware needs and time spent restoring Ghost images, but a few managers are still dubious, and are afraid we might "miss some hardware issues" if we go that route.
"Live Free or Die." Don't like it? Then keep out of the USA
Virtualization looks like necessary evil, because we are incompetent to write better OSes and Application. Virtualization is the easier route.
It's not a question of "competence", there simply is no such thing as a uniformly "better" operating system or application. DOS, for example, is an excellent operating system for some narrow set of applications, and you can hack Mach or Singularity until the cows come home and you're not going to create something better.
I would have preferred a better, from the ground-up OS any day. Hurd, or ever better Singularity!
People like you are part of the reason why software sucks so badly: you simply don't understand real-world tradeoffs. People like you design systems like Mach or Windows, systems that try to be everything to everybody; people like you throw in MLOCs of useless features and generalizations and extensibility, and all you are doing is create bigger and bigger headaches.
Virtualization is doing the right thing: it lets people focus on creating operating systems and server configurations that focus on solving specific problems. Maybe with virtualization, we can finally kill the general purpose operating system.
Virtualisation is an inevitable step in the evolution of computers. It follows the trend that we've already seen - when computers got powerful enough to usefully run more than one process/program at a time, we introduced multitasking operating systems that "virtualised" memory, IO, and peripherals to multiple processes. Now computers are getting powerful enough to usefully run more than one OS at a time, we are seeing software which arbitrates this in much the same way, and extra hardware features to support it better.
Don't forget that this is just the first or second generation of this technology; in future we are likely to see multiple operating systems on one machine become much more commonplace, and as operating systems start to be built with this in mind, increased inter-OS communication in the same way that we have inter-process communication now.
Also worth noting is that we're moving away from the model of ramping up the clock speed on CPUs and moving towards a model of increasing the number of processing cores (dual-core CPUs and SMP), and smart high-speed switched buses (e.g. PCI express, 1/10/100GBps switched ethernet) - I believe that the computers of 10 to 20 years from now will be highly parallel, modular, hot-pluggable sets of processors and buses that will be able to intelligently allocate and partition resources between OSes and apps, and we will see a break away from the strict two-tier OS/program model and move more towards a much more flexible model with multiple levels of abstraction.
How about failover?
Planned upgrades?
Maybe your redundancy worked, but now requires a shutdown to repair? (Think blade servers).
Maybe the customer wants more power and the current system they're on is maxed?
The live migration in Xen has less than half a second of down time, didn't take much to implement, and solves the problem of squeamish customers who don't want any downtime for any reason.
It makes another option to get around shit that can happen.
Most of the time I see people using virtualization, it is to get around software conflicts, or to be able to install things side-by-side that aren't designed to be run in that environment. In such cases, virtualization is overkill. They didn't mean to virtualize the entire processor and memory - they only needed to virtualize the system configuration and limited parts of the file system hierarchy.
For these purposes, chroot is a better fit.
I've often wanted an equivalent for Windows, where I could run an application with a virtual registry, so that it didn't muck things up. Or so that it thought it had full access to the C:\WINDOWS folder. Instead, I have to use Virtualization s which requires 2 gigs of space, causes a 2:1 speed reduction, and cuts my available memory in half.
Even better yet, would be decent installers and applications that follow the rules.