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12-19-2009, 05:30 AM #26Web Hosting Guru
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Not necessarily. Memory accounting on Linux is actually quite a complex matter. OpenVZ's user bean counters tried to simplify it for each VE, but at the end it is not really doing an optimal job...
VSZ is the virtual memory size of your process -- that includes the memory that has been allocated, process/thread stack, shared library etc. It's closely related to privvmpages (allocated pages) but the readings from `ps aux` is not that accurate due to shared libraries.
RSS is the residential memory, i.e. the actual physical memory used by this process. It should be corresponding to the held amount in oomguarpages in a non-overselling/non-swapping scenario. I think if your process gets swapped out on the physical server, RSS will reduce, but oomguarpages will actually stay the same (which is when your physpages is different from oomguarpages).
And although beancounters are tracking two metrics (privvmpages/guaranteed and oomguarpages/burstable), I think there is really pointless to track the GUARANTEED memory due to the ability to swap on the host node. The "guaranteed" amount there is only to guarantee that your processes will not be killed during an OOM event. It can go above the barrier amount as long as the server does not run out of memory (OOM). HOWEVER, in order to reach an OOM event on a Linux server, you usually have to exhaust all the physical memory AND all the swap -- which by then the whole server will be extremely slow anyway and your processes are about as good as dead...
Therefore -- just worry about the burstable memory Remember that's the amount your processes "allocated" rather than "used". So for programs doing slab allocation can usually kill the whole system as they allocate a lot more than they use (i.e. Java). Multi-threaded apps also use a lot more memory on OpenVZ as each thread has default 8MB stack on Linux, which again is allocated but rarely used.
Yeah. Pick Xen or KVM if you can.
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12-19-2009, 06:24 AM #27Web Hosting Evangelist
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Everyone is choosing Xen Is there anyone out there who wants to use OpenVZ?
Learning...
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12-19-2009, 06:36 AM #28Web Hosting Master
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Xen
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12-19-2009, 07:07 AM #29Not so experienced
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Xeeeeeeeeen!!!
Although OpenVZ could be alright for a temp VPS (for testing or something) as it's cheap.
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12-19-2009, 07:18 AM #30VPS Like a Boss!
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It depends how you intend to you the VPS both system has their own advantages and disadvantages, but i assuming i can only keep one for my own use i'll prefer Xen VPS.
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12-19-2009, 07:20 AM #31Temporarily Suspended
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Xen for me
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12-20-2009, 10:39 AM #32Web Hosting Guru
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+1 for xen
- do it your self.
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12-20-2009, 07:25 PM #33Aspiring Evangelist
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Seems most admins here want XEN, why openvz are the majority is WHT VPS offers?
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12-20-2009, 07:33 PM #34Web Hosting Evangelist
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12-20-2009, 08:09 PM #35Retired Moderator
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Cheaper how? They're both free. Easier to oversell, definitely, but then overselling isn't necessarily a problem in itself. Overloading and mismanagement will cause problems on any platform.
OpenVZ is more like shared hosting in its resource allocations so it can give hosts more profit and give users more bang-per-buck. Check the benchmarks thread if you don't believe this. The major downside (as with shared hosting) is the risk of another user taking too much of the shared resource pool and affecting other VPSs. The solution (as with shared hosting) is good management / monitoring by the provider.
Another quite separate issue with OpenVZ is the arcane UBC memory management that hardly any users seem to understand, so they may end up getting less than they expect. Then again, if they're expecting something equivalent to a dedicated server for $5 per month they're going to be disappointed anyway...
Shared hosting - OpenVZ - Xen/KVM etc. all have their place. Users can choose whatever suits their needs.Chris
"Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them." - Laurence J. Peter
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12-20-2009, 09:26 PM #36Web Hosting Master
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Greetings:
Xen and VMWare over OpenVZ; all three are free.
Thank you.
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12-20-2009, 11:17 PM #37Temporarily Suspended
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12-21-2009, 12:57 PM #38Web Hosting Master
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Greetings:
It all comes down to packaging.
Thank you.
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12-21-2009, 10:30 PM #39Web Hosting Master
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Virtuozzo has alot less overheads compared to XEN.
IMHO, for most applications, Virtuozzo would deliver better performance.
How many clients want to install their own kernel or configure a SWAP?
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12-21-2009, 10:49 PM #40Private Citizen
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12-21-2009, 10:49 PM #41Private Citizen
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12-21-2009, 11:47 PM #42Web Hosting Master
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Well if the client is simply looking at installing applications, openVZ would also deliver better performance (lesser overhead).
For the same number of nodes per server, OpenVZ may perform better.
The additional virtualization overhead that comes with XEN, may only be desired of the client truly wishes to deal with the operating system layer - such as the kernel.init.me - Build, Share & Embed
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12-21-2009, 11:54 PM #43Private Citizen
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12-22-2009, 12:09 AM #44Problem Solver
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I prefer xen, because I find it less restricted in what you can and can't do.
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12-22-2009, 01:24 AM #45Location = SoapBox
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even if this were true, a customer is still reliant on their upstream to not oversell the hell out of the server and leave them competing for resources..
How many clients want to install their own kernel or configure a SWAP?
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12-22-2009, 01:51 AM #46Location = SoapBox
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12-22-2009, 02:14 AM #47Web Hosting Master
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Of course. Carefully choosing your provider is important.
Isnt this what managed services are supposed to cover? I know if we asked our clients to install their own kernel or configure swap, they would likely look at us pretty funny .
Yes, there may be providers out there that slap a premium to do this for them, but why deal with that when the Virtualization platform can take care of that for you?
IMHO - I feel there is a virtualization market out there for customers that wish to have the kernel layer abstracted from them, yet want the full advantages of a dedicated server (custom applications, etc)
doesnt mean you can just neglect the benefits of real virtualization and attempt to claim that somehow there is an advantage to software level virtualization because a customer doesnt need to install their own kernel.. sure, its easier for the provider to manage this way - but, I am not so sure its better for the clients - I guess it depends on what customers are after.. but, to use your cost-benefit analysis - it would not be overly difficult to present an alternate analysis here.
IMHO, XEN adds alot of overhead with their HyperVisor layer. My experience comes from the Windows side of the market, and Microsoft has been pushing for granularity in their operating system. This means, the operating system itself would be able to set limits on processor utilization and memory space
Why use a HyperVisor for that?
It is debate-able, even in the Linux front, that XEN's HyperV can do a better job at process, IO and memory scheduling then the Linux kernel. In one study I read, cache misses were far more common on XEN, compared to a Linux Kernel - suggesting that XEN may not be doing the most efficient job in process scheduling. I'd argue the same would apply to memory and disk I/O. Let us think of it this way - the Windows or Linux kernel has direct access to the system's process queue, and can choose the best way to schedule usage of the CPU or the disk. With a HyperVisor such as XEN in between, alot of this is hidden from it, and it has to decide what Operating System rather than process to schedule first (please correct me if I am wrong).
Hence, XEN will always represent an overhead compared to OS-level virtualization. Yes, there are advantages to this - it provides complete OS-level isolation. BUT, I would argue, with Operating System design becoming more granular, these sand-boxes could also be created on the system itself, without the overheads of a 3rd party HyperVisor. This is the philosophy of OpenVZ or Virtuozzo. And it too, IMO, is Real Virtualization.Last edited by Yash-JH; 12-22-2009 at 02:18 AM.
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12-22-2009, 03:18 AM #48Web Hosting Evangelist
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A proper managed environment includes the kernel. One size fits all does not exist with managed dedicated servers, the same applies here. If a customer is purchasing a managed VPS from a reputable company, the company can afford to not be lazy, and manage the kernel level as well. Minor kernel tweaks can drastically improve performance among other things, not to mention more flexibility when it comes to running a more recent kernel. Most quality managed providers include this support in their base management packages. It is not a premium feature by any means in the quality managed hosting arena.
For true isolation, and the ability to run multiple guests with different OSs with consistent performance not dependent on a company seeking a profit (MS/Windows)? Am I the only one that finds it humorous that MS has just started toating "granularity"...sorry couldn't help myself
In all fairness, this is truly debatable. There is has been, and to this day is ongoing optimization with xen's scheduling. Which study do you speak of? This is pretty bold statement, and I would be interested to see the extent of the research.
It depends what on one's definition of "real virtualization." In my eyes Virtuozzo will always be a doctored up jail/chroot environment. It is good at what it does, and certainly has a place in the market. At the same time, soft allocation of resources certainly leaves the door open for the class of overselling that this industry has been plagued with. Thankfully Parallels charges decent coin for Virtuozzo (surprise surprise here eh? ), keeping a good amount of the kiddy hosts from getting their hands on Virtuozzo.Last edited by johringer; 12-22-2009 at 03:31 AM.
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12-22-2009, 04:04 AM #49Newbie
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The most important thing is, customer choose Xen more than OpenVZ.
Why? This is because of Xen standalone kernel, RAM and applications.
We have received a lot of Xen Linux VPS request from our customers.
Then start to offer Xen Linux VPS services to our customers.
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12-22-2009, 04:23 AM #50Problem Solver
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Doesn't help when a well known managed vps provider has this kernel running:
2.6.9-023stab044.11-enterprise #1 SMP Sun Sep 30 12:15:39 MSD 2007 i686 athlon i386 GNU/Linux
which doesn't patch for http://cve.mitre.org/cgi-bin/cvename...=CVE-2009-3547Steven Ciaburri | Industry's Best Server Management - Rack911.com
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