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  • How to manage many mobile device users at server side?

    - by Rami
    I built a social Android application in which users can see other users around them by GPS location. At the beginning thing went well as I had low number of users, but now that I have increasing number of users (about 1500 +100 every day) it has revealed a major problem in my design. In my Google App Engine servlet I have static HashMap that holds all the users profiles objects, currently 1500 and this number will increase as more users register. Why I'm doing it? Every user that requests for the users around him compares his GPS with other users and checks if they are in his 10km radius. This happens every five minutes on average. Consequently, I can't get the users from db every time because GAE read/write operation quota will tear me apart. The problem with this design is? As the number of users increases, the Hashmap turns to null every 4-6 hours, I think that this time is getting shorter, but I'm not sure. I'm fixing this by reloading the users from the db every time I detect that it becomes null, but this causes DOS to my users for 30 sec, so I'm looking for better solution. I'm guessing that it happens because the size of the hashmap. Am I right? I have been advised to use a spatial database, but that means that I can't work with GAE any more and it means that I need to build my big server all over again and lose my existing DB. Is there something I can do with the existing tools? Thanks.

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  • Creating a Corporate Data Hub

    - by BuckWoody
    The Windows Azure Marketplace has a rich assortment of data and software offerings for you to use – a type of Software as a Service (SaaS) for IT workers, not necessarily for end-users. Among those offerings is the “Data Hub” – a  codename for a project that ironically actually does what the codename says. In many of our organizations, we have multiple data quality issues. Finding data is one problem, but finding it just once is often a bigger problem. Lots of departments and even individuals have stored the same data more than once, and in some cases, made changes to one of the copies. It’s difficult to know which location or version of the data is authoritative. Then there’s the problem of accessing the data. It’s fairly straightforward to publish a database, share or other location internally to store the data. But then you have to figure out who owns it, how it is controlled, and pass out the various connection strings to those who want to use it. And then you need to figure out how to let folks access the internal data externally – bringing up all kinds of security issues. Finally, in many cases our user community wants us to combine data from the internally sources with external data, bringing up the security, strings, and exploration features up all over again. Enter the Data Hub. This is an online offering, where you assign an administrator and data stewards. You import the data into the service, and it’s available to you - and only you and your organization if you wish. The basic steps for this service are to set up the portal for your company, assign administrators and permissions, and then you assign data areas and import data into them. From there you make them discoverable, and then you have multiple options that you or your users can access that data. You’re then able, if you wish, to combine that data with other data in one location. So how does all that work? What about security? Is it really that easy? And can you really move the data definition off to the Subject Matter Experts (SME’s) that know the particular data stack better than the IT team does? Well, nothing good is easy – but using the Data Hub is actually pretty simple. I’ll give you a link in a moment where you can sign up and try this yourself. Once you sign up, you assign an administrator. From there you’ll create data areas, and then use a simple interface to bring the data in. All of this is done in a portal interface – nothing to install, configure, update or manage. After the data is entered in, and you’ve assigned meta-data to describe it, your users have multiple options to access it. They can simply use the portal – which actually has powerful visualizations you can use on any platform, even mobile phones or tablets.     Your users can also hit the data with Excel – which gives them ultimate flexibility for display, all while using an authoritative, single reference for the data. Since the service is online, they can do this wherever they are – given the proper authentication and permissions. You can also hit the service with simple API calls, like this one from C#: http://msdn.microsoft.com/en-us/library/hh921924  You can make HTTP calls instead of code, and the data can even be exposed as an OData Feed. As you can see, there are a lot of options. You can check out the offering here: http://www.microsoft.com/en-us/sqlazurelabs/labs/data-hub.aspx and you can read the documentation here: http://msdn.microsoft.com/en-us/library/hh921938

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  • What kind of hosting do I need?

    - by Robert Smith
    I migrated this question from serverfault. Hopefully this is the appropriate place. I have been trying to answer this question but I haven't found an specific answer to my situation. As I want to pay for what I need, I thought I could get a good answer here. I have a custom made forum (rather than a built-in forum like the ones you can find in plugins, e.g. WP-Forum or phpBB type of software) in Django. I don't want to use Apache and modwsgi because it's usually very memory-hungry and I can't afford a big server. I prefer a combination of nginx and gunicorn which I think is very efficient (maybe you can also tell me what you think about that). I'm expecting to receive 10,000 to 20,000 visits each month with 15,000 to 30,000 page impressions. I have reviewed some cloud services like Amazon EC2 or Rackspace and other more traditional services (Linodo). This site won't use videos or big images and I certainly don't need a huge amount of bandwidth (200GB would be definitely too much). I need shell access so shared hosting is out of the question. What do I need to run a website like that without problems? What about RAM? 256MB would be enough (that's the amount of RAM offered by small instances in Amazon and Rackspace)? Do you know of any alternative to those I mentioned? If you need more information to provide a useful answer, please don't hesitate to ask. By the way, I was told that Linodo is not all that different to Amazon EC2 but this website is supposed to work 24/7, so I can't take advantage of Linodo's flexibility regarding creating and deleting instances. Thanks in advance.

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  • April 25th Online Forum -- Oracle Solaris 11: What's New Since the Launch

    - by Larry Wake
    It's been a few months since we released Oracle Solaris 11, so we thought it was time to check in and let you know how things are going. On April 25th, at 9:00 PT, we'll host an online forum, featuring Markus Flierl, the VP for Solaris core engineering, as well as engineers, customers and partners. During the forum, Markus and his crew will give an update on the release, recap Oracle's OS strategy, and give you a peek at what the engineers are working on for future updates. I think one of the more interesting parts of this event will be the chance for some of our customers to share why they've moved to Oracle Solaris 11 and what benefits it has already given them.  We'll also have an online chat, so you can ask Solaris engineers any questions about what you've heard, or other thoughts you've had.  It should be a worthwhile event -- hope you can join us. Online Forum: Oracle Solaris 11: What’s New Since the LaunchApril 25th 9:00 a.m. PDT – 11:30 a.m. PDTRegister today!

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  • Hosting and scaling of a facebook application on cloud?

    - by DhruvPathak
    We would be building a facebook application in django(Python), but still not sure of where to host it economically,and with a good provision to scale in case the app gets viral. Some details about the app: i) Would be HTML based like a website,using django as a framework. ii) 100K is the number of expected pageviews in a day,if the app is viral. iii) The users will not generate any media content,only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment,cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost ? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. ( Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management ? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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  • No proper kmeans clustering of images in matlab

    - by user3237134
    I am having 1200 face images in my training set.There are 2989 test face images. I am using eigen faces (PCA) for feature extraction. I am using kmeans clustering. Source code I tried: IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); Problem: Images are not clustered properly. Same faces should be clustered. But different faces are being clustered. Questions: Should I have to use still more face images for training? How accuracy of clustering can be achieved? What is the solution?

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  • Any frameworks or library allow me to run large amount of concurrent jobs schedully?

    - by Yoga
    Are there any high level programming frameworks that allow me to run large amount of concurrent jobs schedully? e.g. I have 100K of urls need to check their uptime every 5 minutes Definitely I can write a program to handle this, but then I need to handle concurrency, queuing, error handling, system throttling, job distribution etc. Will there be a framework that I only focus on a particular job (i.e. the ping task) and the system will take care of the scaling and error handling for me? I am open to any language.

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  • How to rewrite a TCP MMOG server designed to run in a single machine, in a distributed way?

    - by Dokkat
    I have a MMOG server running on C++, using winsockets. My server won't support more than 200 players. I had the idea of redesigning it so it will use multiple servers instead of one, so, maybe, for example, each server could take care of a number of players, and, if it was too laggy, it could transfer the responsability of that player to other server. I'm not sure of how to program a consistent game logic like that, though. Are there techniques for this?

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  • Hosting and scaling a Facebook application in the cloud? [migrated]

    - by DhruvPathak
    We would be building a Facebook application in Django (Python), but still not sure of where to host it economically, and with a good provision to scale in case the app gets viral. Some details about the app: Would be HTML based like a website,using django as a framework. 100K is the number of expected pageviews in a day, if the app is viral. The users will not generate any media content, only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on Google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment, cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. (Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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  • Combine auto-syncing cloud and VCS

    - by ComFreek
    This question brought me to another question: is there any VCS/tool for a VCS which automatically backups your source code between the last checkout and current changes? I had the problem of loosing uncommited source code changes just one week ago. I did not want to commit yet because the changes were incomplete. But then, an error when moving the data to an USB stick caused the data loss. That's the opposite what a cloud service (like Google Drive, SkyDrive, DropBox, ...) does: it tracks each change you made! Have you lost your data? That's no problem because you have the latest version online. So what would a combined solution look like? It would offer full functionality of a VCS including auto-syncing of any intermediate changes between two commits/checkouts to a temporary online location.

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  • Use a custom value object or a Guid as an entity identifier in a distributed system?

    - by Kazark
    tl;dr I've been told that in domain-driven design, an identifier for an entity could be a custom value object, i.e. something other than Guid, string, int, etc. Can this really be advisable in a distributed system? Long version I will invent an situation analogous to the one I am currently facing. Say I have a distributed system in which a central concept is an egg. The system allows you to order eggs and see spending reports and inventory-centric data such as quantity on hand, usage, valuation and what have you. There area variety of services backing these behaviors. And say there is also another app which allows you to compose recipes that link to a particular egg type. Now egg type is broken down by the species—ostrich, goose, duck, chicken, quail. This is fine and dandy because it means that users don't end up with ostrich eggs when they wanted quail eggs and whatnot. However, we've been getting complaints because jumbo chicken eggs are not even close to equivalent to small ones. The price is different, and they really aren't substitutable in recipes. And here we thought we were doing users a favor by not overwhelming them with too many options. Currently each of the services (say, OrderSubmitter, EggTypeDefiner, SpendingReportsGenerator, InventoryTracker, RecipeCreator, RecipeTracker, or whatever) are identifying egg types with an industry-standard integer representation the species (let's call it speciesCode). We realize we've goofed up because this change could effect every service. There are two basic proposed solutions: Use a predefined identifier type like Guid as the eggTypeID throughout all the services, but make EggTypeDefiner the only service that knows that this maps to a speciesCode and eggSizeCode (and potentially to an isOrganic flag in the future, or whatever). Use an EggTypeID value object which is a combination of speciesCode and eggSizeCode in every service. I've proposed the first solution because I'm hoping it better encapsulates the definition of what an egg type is in the EggTypeDefiner and will be more resilient to changes, say if some people now want to differentiate eggs by whether or not they are "organic". The second solution is being suggested by some people who understand DDD better than I do in the hopes that less enrichment and lookup will be necessary that way, with the justification that in DDD using a value object as an ID is fine. Also, they are saying that EggTypeDefiner is not a domain and EggType is not an entity and as such should not have a Guid for an ID. However, I'm not sure the second solution is viable. This "value object" is going to have to be serialized into JSON and URLs for GET requests and used with a variety of technologies (C#, JavaScript...) which breaks encapsulation and thus removes any behavior of the identifier value object (is either of the fields optional? etc.) Is this a case where we want to avoid something that would normally be fine in DDD because we are trying to do DDD in a distributed fashion? Summary Can it be a good idea to use a custom value object as an identifier in a distributed system (solution #2)?

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  • Collaborative Filtering Techniques

    - by user95261
    Good Day! I am in need of help about collaborative filtering techniques implementation in predicting psychopathy of twitter users. I have two data set, training set and test set. Training set users have already scores in psychopathy, I need any collaborative filtering techniques to predict scores of test set users. Collaborative Filtering such as Item/User-Based CF, Bayesian Belief Nets, Clustering, Latent Semantic, etc. Please help me. :( I am very confused on how to implement any of these. Thank you!

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  • Do you I think I should integrate something like AWS or other cloud service from the initial phases of my project?

    - by Kareem Ergawy
    Do you I think I should integrate something like AWS or other cloud service from the initial phases of my project or I should be working on the front and back end components regularly and integrate AWS later? I am starting to work on a mobile service. From day one, I wish to make sure that my service will be scalable and able to handle large loads of requests. This is my first time in architecting a large scale system from the beginning so I can't decide what is best.

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  • Efficient algorithm for Virtual Machine(VM) Consolidation in Cloud

    - by devansh dalal
    PROBLEM: We have N physical machines(PMs) each with ram Ri, cpu Ci and a set of currently scheduled VMs each with ram requirement ri and ci respectively Moving(Migrating) any VM from one PM to other has a cost associated which depends on its ram ri. A PM with no VMs is shut down to save power. Our target is to minimize the weighted sum of (N,migration cost) by migrating some VMs i.e. minimize the number of working PMs as well as not to degrade the service level due to excessive migrations. My Approach: Brute Force approach is choosing the minimum loaded PM and try to fit its VMs to other PMs by First Fit Decreasing algorithm or we can select the victim PMs and target PMs based on their loading level and shut down victims if possible by moving their VMs to targets. I tried this Greedy approach on the Data of Baadal(IIT-D cloud) but It isn't giving promising results. I have also tried to study the Ant colony optimization for dynamic VM consolidating but was unable to understand very much. I used the links. http://dumas.ccsd.cnrs.fr/docs/00/72/52/15/PDF/Esnault.pdf http://hal.archives-ouvertes.fr/docs/00/72/38/56/PDF/RR-8032.pdf Would anyone please clarify the solution or suggest any new approach/resources for better performance. I am basically searching for the algorithms not the physical optimizations and I also know that many commercial organizations have provided these solution but I just wanted to know more the underlying algorithms. Thanks in advance.

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  • What is lightweight lock in distributed shared memory systems?

    - by Kutluhan Metin
    I started reading Tanenbaum's Distributed Systems book a while ago. I read about two phase locking and timestamp reordering in transactions chapter. While having a deeper look from google I heard of lightweight transactions/lightweight transactional memory. But I couldn't find any good explanation and implementation. So what is lightweight memory? What are the benefits of lightweight locks? And how can I implement them?

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  • Where do you earn more money (Autonomous Systems vs Distributed Systems)? [closed]

    - by Puckl
    I am interested in both topics and I can choose between them for my computer science master. I think the distributed systems master focuses more on software technologies and the autononmous systems master is focused on robotics and machine learning. Do you get good jobs in the fild of machine learning without a Ph.D.? I guess there are more jobs available in the Software-Tech world, is this right? Where do you earn more money? (It is not the only criteria, but it matters)

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  • Storing Projects on Google Drive (Cloud)

    - by JamesKraw
    I've started using Google Drive for my cloud needs and backing up pretty much everything. I've got the app installed so it auto-sync's all my content in most things. My question is this, I am currently coding for iOS (although this applies to any coding project) and am split on storing my project files on Google Drive while using sync. My theory is that if I did use it, I'd never have to worry about system crashes or lost code before backups, but if I do use it it will be sync'ing a-lot and I thought there might be problems with it detecting changes and trying to sync for example half way through compiling. Bandwidth isn't an issue as I have fast connection and unlimited monthly allowance. Has anyone ever used this, or similar cloud-based sync'ing (dropbox etc) for this and knows whether it works or not or whether there are any potential problems etc.

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  • Computing complex math equations in python

    - by dassouki
    Are there any libraries or techniques that simplify computing equations ? Take the following two examples: F = B * { [ a * b * sumOf (A / B ''' for all i ''' ) ] / [ sumOf(c * d * j) ] } where: F = cost from i to j B, a, b, c, d, j are all vectors in the format [ [zone_i, zone_j, cost_of_i_to_j], [..]] This should produce a vector F [ [1,2, F_1_2], ..., [i,j, F_i_j] ] T_ij = [ P_i * A_i * F_i_j] / [ SumOf [ Aj * F_i_j ] // j = 1 to j = n ] where: n is the number of zones T = vector [ [1, 2, A_1_2, P_1_2], ..., [i, j, A_i_j, P_i_j] ] F = vector [1, 2, F_1_2], ..., [i, j, F_i_j] so P_i would be the sum of all P_i_j for all j and Aj would be sum of all P_j for all i I'm not sure what I'm looking for, but perhaps a parser for these equations or methods to deal with multiple multiplications and products between vectors? To calculate some of the factors, for example A_j, this is what i use from collections import defaultdict A_j_dict = defaultdict(float) for A_item in TG: A_j_dict[A_item[1]] += A_item[3] Although this works fine, I really feel that it is a brute force / hacking method and unmaintainable in the case we want to add more variables or parameters. Are there any math equation parsers you'd recommend? Side Note: These equations are used to model travel. Currently I use excel to solve a lot of these equations; and I find that process to be daunting. I'd rather move to python where it pulls the data directly from our database (postgres) and outputs the results into the database. All that is figured out. I'm just struggling with evaluating the equations themselves. Thanks :)

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  • hyperv machine guest loads slow

    - by Dani Avni
    this is by far one of the strangest things I have seen. I have a win 2008R2 cluster with a CSV. the CSV itself is on an iSCSI storage (hitachi HUS 110) basic config of the two hosts in the cluster is Dell R610 Win 2008 R2 with all patches 64GB 1 NIC for host access 2 NICs for guest access 2 NICs for iSCSI these machine work great and I can load a 2008R2 test guest machine on them in less than 90 seconds after the above config is running for over a year, I now need to add a new host. now the host is Dell R620 (Still intel but different CPU) Win 2008 R2 with all patches 64GB 1 NIC for host access 2 NICs for guest access 2 NICs for iSCSI I added this new host to the domain and to the cluster, I gave it access to the CSV and I tried loading the same guest machine that loads in 90 seconds in the other hosts. the machine loads in about 6 minutes. no matter how many times I try this the old hosts load the machine in about 90 seconds and this new host in around 6 minutes to eliminate any problems with the iSCSI connection, I added a new LUN and directly accessed it from the new host and I was working at around 300MB/s so no problem there. I also tested the connection between the other hosts and the new one and network is working fine there too. to eliminate problems in HyperV, I copied the machine to the local disk of the new host and it loaded in less than 20 seconds. now is the point were things get a lot stranger: in my tests I tried installing a fresh windows guest machine to the CSV from the new host. I noticed that while the fresh windows was installing, my test guest was loading in less than 90 seconds even on the new host (I repeated this a few times). If I paused the fresh install guest and tried loading the test guest again it loaded in 6 minutes. and again after I resumed the guest installation the test guest loaded fast. after the fresh windows was also loaded, I ran tests loading the fresh window and my test machine. each one of them loaded in about 5 minutes when I tried loading them separately. however when I started both of them in the same time they both loaded in around 2.5 minutes it seems that the iSCSI disk access is only working if it is under some load (although I never got to above 10% utilization according to the task manager) does anyone have any idea what could be the problem?

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  • How to script printer creation on a Windows Server 2008 R2 clustered print server?

    - by Massimo
    As per subject. I've found some ways of scripting printer creation on Windows print servers using WMI, but it looks like WMI doesn't support clustered print servers (or clustered servers at all). The scripts in C:\Windows\System32\Printing_Admin_Scripts are useless because, they are not cluster-aware and end up creating the printers on the active cluster node (just like using WMI). The only tool I found that was able to work on a clustered print server is printui.exe (shortcut for rundll32 printui.dll, PrintUIEntry), but it can't create TCP printing ports: it can only add printers if the port already exists. How can I completely script printer creation (including TCP printing ports!) on a clustered Windows Server 2008 R2 print server?

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  • Apache mod_wsgi elegant clustering method

    - by Dr I
    I'm currently trying to build a scalable infrastructure for my Python webservers. Actually, I'm trying to find the most elegant way to build a scalable cluster to host all my Python WebServices. For now, I'm using three servers like this: 1 x PuppetMaster to deploy my servers. 2 x Apache Reverse Proxy Front-end servers. 1 x Apache HTTPd Server which host the Python WSGI Applications and binded to using mod_wsgi. 4 x MongoDB Clustered server. Everything is OK concerning the Reverse proxy and the DB Backend, I'm able to easily add a new Reverse Proxy and a new DB Node, but my problem is about the Python WebServer. I thinked to just provision a new node with exactly the same configuration and a rsync replication between the two nodes, but It's not really usefull in term of deployement for my developpers etc. So if you have a solution which is as efficient and elegant that the Tomcat Cluster I'll be really happy to ear it ;-)

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  • how to proxy sql queries (INSERT, UPDATE e.t.c.)

    - by XakRu
    I have installed cluster MYSQL (galley with mariadb) As an application server installed Apache. on a server with Apache installed haproxy which proxies requests from php in this case installed for zabbix server cluster. But faced with deadlocks, now I want to proxy requests WRITE, INSERT, UPDATE to the second server. SELECT queries to the second and third server. I would be happy to see your suggestions. Please do not write: use mysql - proxy. I want to see what program it may to proxy SQL requests. scheme: http://www.gliffy.com/pubdoc/4474830/L.png

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  • Setting up Cluster Configuration using an existing web server as a Primary Node?

    - by RapidWebs
    Thanks in advance for any help which is issued! I am having a slight issue, and need help with the decision making process when it comes to setting up my Cluster Configuration, consisting on a line of Ubuntu Servers (12.04). We currently have a Primary node, which resides in the US within a Datacenter, but we are going to be using this for all serious bandwidth and resource intensive websites, and through a configuration of Virtualmin + Webmin, will be setup as a sort of pseudo-cluster, using Virtualmins Cluster Modules. Anyways, on to the issue: We also have a business line setup locally, with three servers. here are their specs: Intel P4 2.4 ghz, 1GB Ram, 110 gb sata, Ubuntu 12.04* AMD 1.3 ghz, 512MB Ram, 20 GB IDE P3 Xeon 800mhz (dual physical processors), 1GB Ram, 3 * 25 GB Raid Configuration (one in use for host operating system). The first machine is currently IN USE and is serving virtual hosts off a sub-domain. My question is this: How can I integrate the Secondary node (which will be the Primary node per say, in this smaller configuration...) which is currently in use, into the cluster configuration w/ the other two servers for: Sharing Resources Redundancy (HA?) NFS /w the two Raid Disks without having the FORMAT the secondary node, and start fresh moving all my services in to a DRBD network drive or something similar, and than restoring all active virtualmin's Virtual hosts. the idea is that I want minimal downtime to people currently being served from server2.mywebsite.com, and from what I understand, all services need to be on a NFS so that they can be mounted on demand and accessed from the other machine taking over (i.e. Heartbeat + DRBD Config.) but my issue is that i already have all these services installed to their default directory structure: how can i most easily setup this NFS and HA system, move all my desires services to this new drive, and do it with minimal down time, and without breaking Virtualmin and everything else on my server? even just some pointers, a thread i could read, or a step by step check list or run down of commands i could issue to get started would be great! thanks!

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  • NTRU Pseudo-code for computing Polynomial Inverses

    - by Neville
    Hello all. I was wondering if anyone could tell me how to implement line 45 of the following pseudo-code. Require: the polynomial to invert a(x), N, and q. 1: k = 0 2: b = 1 3: c = 0 4: f = a 5: g = 0 {Steps 5-7 set g(x) = x^N - 1.} 6: g[0] = -1 7: g[N] = 1 8: loop 9: while f[0] = 0 do 10: for i = 1 to N do 11: f[i - 1] = f[i] {f(x) = f(x)/x} 12: c[N + 1 - i] = c[N - i] {c(x) = c(x) * x} 13: end for 14: f[N] = 0 15: c[0] = 0 16: k = k + 1 17: end while 18: if deg(f) = 0 then 19: goto Step 32 20: end if 21: if deg(f) < deg(g) then 22: temp = f {Exchange f and g} 23: f = g 24: g = temp 25: temp = b {Exchange b and c} 26: b = c 27: c = temp 28: end if 29: f = f XOR g 30: b = b XOR c 31: end loop 32: j = 0 33: k = k mod N 34: for i = N - 1 downto 0 do 35: j = i - k 36: if j < 0 then 37: j = j + N 38: end if 39: Fq[j] = b[i] 40: end for 41: v = 2 42: while v < q do 43: v = v * 2 44: StarMultiply(a; Fq; temp;N; v) 45: temp = 2 - temp mod v 46: StarMultiply(Fq; temp; Fq;N; v) 47: end while 48: for i = N - 1 downto 0 do 49: if Fq[i] < 0 then 50: Fq[i] = Fq[i] + q 51: end if 52: end for 53: {Inverse Poly Fq returns the inverse polynomial, Fq, through the argument list.} The function StarMultiply returns a polynomial (array) stored in the variable temp. Basically temp is a polynomial (I'm representing it as an array) and v is an integer (say 4 or 8), so what exactly does temp = 2-temp mod v equate to in normal language? How should i implement that line in my code. Can someone give me an example. The above algorithm is for computing Inverse polynomials for NTRUEncrypt key generation. The pseudo-code can be found on page 28 of this document. Thanks in advance.

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  • SAP se lance dans le Cloud Computing et présente la première application de sa nouvelle gamme « On-Demand »

    SAP se lance dans le Cloud Computing Et présente la première application de sa nouvelle génération d'applications « On-Demand » Cette année, la participation de SAP au très prestigieux salon CeBIT s'articule autour de la promotion de la nouvelle génération de ses solutions « On-Demand », alliant la puissance du Cloud Computing à la flexibilité du paiement à l'utilisation en mode SaaS. Pour répondre aux attentes des entreprises qui cherchent aujourd'hui à optimiser leurs processus business et les adapter à leurs métiers sans réinvestir dans leurs systèmes d'informations, SAP introduit une nouvelle gamme de solutions On-Demand, intégrée à la suite logicielle SAP Business Suite.

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