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  • memcached cluster maintenance

    - by Yang
    Scaling up memcached to a cluster of shards/partitions requires either distributed routing/partition table maintenance or centralized proxying (and other stuff like detecting failures). What are the popular/typical approaches/systems here? There's software like libketama, which provides consistent hashing, but this is just a client-side library that reacts to messages about node arrivals/departures---do most users just run something like this, plus separate monitoring nodes that, on detecting failures, notify all the libketamas of the departure? I imagine something like this might be sufficient since typical use of memcached as a soft-state cache doesn't require careful attention to consistency, but I'm curious what people do.

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  • Native arrays and computing hashvalues (VB, C#)

    - by Jeffrey Kern
    I feel bad asking this question but I am currently not able to program and test this as I'm writing this on my cell-phone and not on my dev machine :P (Easy rep points if someone answers! XD ) Anyway, I've had experience with using hashvalues from String objects. E.g., if I have StringA and StringB both equal to "foo", they'll both compute out the same hashvalue, because they're set to equal values. Now what if I have a List, with T being a native data type. If I tried to compute the hashvalue of ListA and ListB, assuming that they'd both be the same size and contain the same information, wouldn't they have equal hashvalues as well?

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  • How to Design Programs: An Introduction to Programming and Computing -- teacher guide access

    - by user295683
    Hello -- I'm a biologist switching careers, and trying to learn programming as a result. I stumbled upon the aforementioned book on Amazon, which jived with my liberal arts background. Despite my great satisfaction with the didactic approach, I was frustrated to see that the answers to the exercises are restricted to teachers only. As I am pursuing this endeavor on my own, this restriction dramatically cripples the value of this book. My request to the author's website for access to the answers has not been answered, and I would desperately like to continue with this book. Anyone have any experience dealing with the book's website, or at the very least a torrent of the answers? Otherwise, I suspect I will be relegated to using JavaScript for everything! Thanks!

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  • Computing, storing, and retrieving values to and from an N-Dimensional matrix

    - by Adam S
    This question is probably quite different from what you are used to reading here - I hope it can provide a fun challenge. Essentially I have an algorithm that uses 5(or more) variables to compute a single value, called outcome. Now I have to implement this algorithm on an embedded device which has no memory limitations, but has very harsh processing constraints. Because of this, I would like to run a calculation engine which computes outcome for, say, 20 different values of each variable and stores this information in a file. You may think of this as a 5(or more)-dimensional matrix or 5(or more)-dimensional array, each dimension being 20 entries long. In any modern language, filling this array is as simple as having 5(or more) nested for loops. The tricky part is that I need to dump these values into a file that can then be placed onto the embedded device so that the device can use it as a lookup table. The questions now, are: What format(s) might be acceptable for storing the data? What programs (MATLAB, C#, etc) might be best suited to compute the data? C# must be used to import the data on the device - is this possible given your answer to #1?

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  • How to JNDI lookup from cluster 1 : a queue that exists in cluster 2 in Websphere 6?

    - by user347394
    I have a Websphere topology wherein in Cluster1, I have an MDB that's trying to publish to another MDB that resides in Cluster2. Since they're both in the same container, I tried simply Blockquote Context ctx = new InitialContext(); ctx.lookup("jms/MyQueue"); Blockquote The "jms/MyQueue" is configured in Cluster2. As you can see, this doesn't work!! 1) Do I have to provide an environment entry while creating the InitialContext? Even though both clusters are part of the same container? 2) If not, how then can I lookup the said queue in Cluster 2?

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  • Computing the scalar product of two vectors in C++

    - by HowardRoark
    I am trying to write a program with a function double_product(vector<double> a, vector<double> b) that computes the scalar product of two vectors. The scalar product is $a_{0}b_{0}+a_{1}b_{1}+...+a_{n-1}b_{n-1}$. Here is what I have. It is a mess, but I am trying! #include <iostream> #include <vector> using namespace std; class Scalar_product { public: Scalar_product(vector<double> a, vector<double> b); }; double scalar_product(vector<double> a, vector<double> b) { double product = 0; for (int i = 0; i <= a.size()-1; i++) for (int i = 0; i <= b.size()-1; i++) product = product + (a[i])*(b[i]); return product; } int main() { cout << product << endl; return 0; }

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  • How to deploy updates to .NET website in cluster

    - by royappa
    We are operating a corporate web application on a load-balanced cluster that consists of two identical IIS servers talking to a single MSSQL database. To deploy updates I am using this primitive process: 1) Make a copy of the entire site folder (wwwroot\inetpub\whatever) on each IIS box 2) Download the updated, compiled files onto each IIS box from our development area 3) Shut down IIS both web servers 4) Copy the new and updated files into the wwwroot folder (overwriting any same files) 5) Then restart IIS on both machines When there are database changes involved there are a few other steps. The whole process is fairly quick but it is ugly and fraught with danger, so it has to be done with full concentration. I would like to just push one button to make it all happen. And I want a one-click rollback in case there is a problem (that's the reason I make the copy in step #1). I am looking for tools to manage and improve this process. If it also helped us maintain a changelog, that would be nice. Thanks.

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  • Computing e^(-j) in C..

    - by Erkan H
    I need to compute imaginary exponential in C. As far as I know, there is no complex number library in C. It is possible to get e^x with exp(x) of math.h, but how can I compute the value of e^(-j), where j = sqrt(-1)?

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  • Computing Form Location with Button

    - by user2934515
    I'm working on a programming assignment, and I'm trying to make this button take the values from two textboxes, and calculate the new location for the form window. I'm having trouble converting the textbox values to type int, and being made usable by the btnCompute_click method. private void btnCompute_Click(object sender, EventArgs e) { int x = Convert.ToInt32(txtXvalue); int y = Convert.ToInt32(txtYvalue); Location = new Point(x,y); } private void xValue_TextChanged(object sender, EventArgs e) { int xValue = Convert.ToInt32(txtXvalue); } private void yValue_TextChanged(object sender, EventArgs e) { int y = Convert.ToInt32(txtYvalue); } I forgot to add some additional info, the acceptable values for x and y must be positive. Would I use an if...else statement to control the acceptable values?

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  • amazon cloud vs rackspace cloud

    - by machaa
    Hi, I'm looking to take a dedicated server - in the process I read about Amazon Cloud computing & Rackspace Cloud Servers. Now I'm not sure which one to opt? Could somebody suggest - Performance & Price wise. Regards

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  • Multi-Boot through IPMI possible?

    - by yoursort
    Hi, I want to setup a cluster. On each machine Windows XP and Linux should be installed and the OS should be selectable by a boat loader (e.g. grub). All machines have IPMI cards. Is it possible when starting the machines over IPMI to also select the OS to boot? And how? Thanks!

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  • What is the differences between a Remote File Share Witness Quorum and a Disk Witness Quorum?

    - by arex1337
    Say you set up a Windows Server Failover Cluster consisting of two nodes, on Windows Server 2008 R2 Enterprise. Now when you want to configure quorum you can use either a remote shared folder, or a shared disk (unless your nodes are separated geographically). I'd love to know more about when to use a disk witness and when to use a file share witness. What are the differences? Does it matter at all?

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  • protecting an application against hardware failure [on hold]

    - by alex
    I have an application for which I am looking for a way to protect against hardware and software (operating system ) failure. Cluster seems OK but the storage become the single point of failure and also I do not have a SAN. Can you please tell me if there are other ways to protect the application? Periodically this application is updated and changes should be replicated automatically to the second server.

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  • Windows DFS File System Clustering

    - by tearman
    We're attempted to set up a high availability network for our file servers, and we're wanting to do a DFS file system cluster using the same back-end storage (our back-end storage has its own clustering mechanisms that it manages itself). The question being, A. how would one go about setting up DFS clustering, and B. how can we get Windows to cooperate with multiple servers accessing the same SAN volumes?

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  • How to run your own cloud network at home?

    - by Xeoncross
    I have 7 PC's around the house that total more than 10Ghz in CPU power. I was wondering if I could put them to use building my own "cloud computing" network to help with rendering videos, blender animations, Photoshop effects, or anything else. Does something like this exists - and if so what is it called and where do I find it?

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  • What is massively parallel processing (MPP) ?

    - by HotTester
    Ever since Microsoft introduced sql-server version code-named "Madison" the massively parallel processing (MPP) has got into picture. What exactly is it and how does sql-server is going to benefit from it ? Further is massively parallel processing (MPP) related to parallel computing ? I read about Madison here and about parallel computing here. Thanks in advance.

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  • jboss cache as hibernate 2nd level - cluster node doesn't persist replicated data

    - by Sergey Grashchenko
    I'm trying to build an architecture basically described in user guide http://www.jboss.org/file-access/default/members/jbosscache/freezone/docs/3.2.1.GA/userguide_en/html/cache_loaders.html#d0e3090 (Replicated caches with each cache having its own store.) but having jboss cache configured as hibernate second level cache. I've read manual for several days and played with the settings but could not achieve the result - the data in memory (jboss cache) gets replicated across the hosts, but it's not persisted in the datasource/database of the target (not original) cluster host. I had a hope that a node might become persistent at eviction, so I've got a cache listener and attached it to @NoveEvicted event. I found that though I could adjust eviction policy to fully control it, no any persistence takes place. Then I had a though that I could try to modify CacheLoader to set "passivate" to true, but I found that in my case (hibernate 2nd level cache) I don't have a way to access a loader. I wonder if replicated data persistence is possible at all by configuration tuning ? If not, will it work for me to create some manual peristence in CacheListener (I could check whether the eviction event is local, and if not - persist it to hibernate datasource somehow) ? I've used mvcc-entity configuration with the modification of cacheMode - set to REPL_ASYNC. I've also played with the eviction policy configuration. Last thing to mention is that I've tested entty persistence and replication in project that has been generated with Seam. I guess it's not important though.

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  • iptable CLUSTERIP won't work

    - by Rad Akefirad
    We have some requirements which explained here. We tried to satisfy them without any success as described. Here is the brief information: Here are requirements: 1. High Availability 2. Load Balancing Current Configuration: Server #1: one static (real) IP for each 10.17.243.11 Server #2: one static (real) IP for each 10.17.243.12 Cluster (virtual and shared among all servers) IP: 10.17.243.15 I tried to use CLUSTERIP to have the cluster IP by the following: on the server #1 iptables -I INPUT -i eth0 -d 10.17.243.15 -j CLUSTERIP --new --hashmode sourceip --clustermac 01:00:5E:00:00:20 --total-nodes 2 --local-node 1 on the server #2 iptables -I INPUT -i eth0 -d 10.17.243.15 -j CLUSTERIP --new --hashmode sourceip --clustermac 01:00:5E:00:00:20 --total-nodes 2 --local-node 2 When we try to ping 10.17.243.15 there is no reply. And the web service (tomcat on port 8080) is not accessible either. However we managed to get the packets on both servers by using TCPDUMP. Some useful information: iptable roules (iptables -L -n -v): Chain INPUT (policy ACCEPT 21775 packets, 1470K bytes) pkts bytes target prot opt in out source destination 0 0 CLUSTERIP all -- eth0 * 0.0.0.0/0 10.17.243.15 CLUSTERIP hashmode=sourceip clustermac=01:00:5E:00:00:20 total_nodes=2 local_node=1 hash_init=0 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 14078 packets, 44M bytes) pkts bytes target prot opt in out source destination Log messages: ... kernel: [ 7.329017] e1000e: eth3 NIC Link is Up 100 Mbps Full Duplex, Flow Control: None ... kernel: [ 7.329133] e1000e 0000:05:00.0: eth3: 10/100 speed: disabling TSO ... kernel: [ 7.329567] ADDRCONF(NETDEV_CHANGE): eth3: link becomes ready ... kernel: [ 71.333285] ip_tables: (C) 2000-2006 Netfilter Core Team ... kernel: [ 71.341804] nf_conntrack version 0.5.0 (16384 buckets, 65536 max) ... kernel: [ 71.343168] ipt_CLUSTERIP: ClusterIP Version 0.8 loaded successfully ... kernel: [ 108.456043] device eth0 entered promiscuous mode ... kernel: [ 112.678859] device eth0 left promiscuous mode ... kernel: [ 117.916050] device eth0 entered promiscuous mode ... kernel: [ 140.168848] device eth0 left promiscuous mode TCPDUMP while pinging: tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 12:11:55.335528 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2390, length 64 12:11:56.335778 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2391, length 64 12:11:57.336010 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2392, length 64 12:11:58.336287 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2393, length 64 And there is no ping reply as I said. Does anyone know which part I missed? Thanks in advance.

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  • Recommendations for distributed processing/distributed storage systems

    - by Eddie
    At my organization we have a processing and storage system spread across two dozen linux machines that handles over a petabyte of data. The system right now is very ad-hoc; processing automation and data management is handled by a collection of large perl programs on independent machines. I am looking at distributed processing and storage systems to make it easier to maintain, evenly distribute load and data with replication, and grow in disk space and compute power. The system needs to be able to handle millions of files, varying in size between 50 megabytes to 50 gigabytes. Once created, the files will not be appended to, only replaced completely if need be. The files need to be accessible via HTTP for customer download. Right now, processing is automated by perl scripts (that I have complete control over) which call a series of other programs (that I don't have control over because they are closed source) that essentially transforms one data set into another. No data mining happening here. Here is a quick list of things I am looking for: Reliability: These data must be accessible over HTTP about 99% of the time so I need something that does data replication across the cluster. Scalability: I want to be able to add more processing power and storage easily and rebalance the data on across the cluster. Distributed processing: Easy and automatic job scheduling and load balancing that fits with processing workflow I briefly described above. Data location awareness: Not strictly required but desirable. Since data and processing will be on the same set of nodes I would like the job scheduler to schedule jobs on or close to the node that the data is actually on to cut down on network traffic. Here is what I've looked at so far: Storage Management: GlusterFS: Looks really nice and easy to use but doesn't seem to have a way to figure out what node(s) a file actually resides on to supply as a hint to the job scheduler. GPFS: Seems like the gold standard of clustered filesystems. Meets most of my requirements except, like glusterfs, data location awareness. Ceph: Seems way to immature right now. Distributed processing: Sun Grid Engine: I have a lot of experience with this and it's relatively easy to use (once it is configured properly that is). But Oracle got its icy grip around it and it no longer seems very desirable. Both: Hadoop/HDFS: At first glance it looked like hadoop was perfect for my situation. Distributed storage and job scheduling and it was the only thing I found that would give me the data location awareness that I wanted. But I don't like the namename being a single point of failure. Also, I'm not really sure if the MapReduce paradigm fits the type of processing workflow that I have. It seems like you need to write all your software specifically for MapReduce instead of just using Hadoop as a generic job scheduler. OpenStack: I've done some reading on this but I'm having trouble deciding if it fits well with my problem or not. Does anyone have opinions or recommendations for technologies that would fit my problem well? Any suggestions or advise would be greatly appreciated. Thanks!

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  • Le service de "Cloud computing" de jeux vidéo OnLive annonce ses dates et son prix à la Game Develop

    Mise à jour du 11/03/10 Le service de "Cloud computing" de jeux vidéo OnLive annonce ses dates et son prix à la Game Developers Conference 2010 Se déroulant actuellement, la Game Developers Conference 2010 a offert l'occasion à Mike McGarvey, responsable du projet OnLive, d'officialiser certains points sur son projet de "could computing" pour les jeux vidéo. On apprend ainsi que le service sera disponible à partir du 17 juin prochain sur la sol américain. Rien n'est précisé quand à sa disponibilité du service en Europe. Le service demandera au client de s'abonner mensuellement pour un prix de 14,95$ (soit environ 11€ par mois). Le service sera dans un p...

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  • Quels sont les avantages du Cloud Computing pour votre entreprise ? Google lance "Go Google Cloud Ca

    Quels sont les avantages du Cloud Computing pour votre entreprise ? Google lance "Go Google Cloud Calculator" pour en appréhender les bénéfices Le cloud computing intéresse de plus en plus d'entreprises, et des millions d'entre elles se sont tournées vers Google en migrant vers les Google Apps. Une décision encore audacieuse, tant il est difficile d'imaginer ce que le travail « dans le nuage » signifie vraiment et quels en sont les véritables avantages. Quel est l'impact de la collaboration en ligne sur votre lieu de travail ? Comment une capacité de stockage d'email accrue ou une messagerie instantanée intégrée et le chat vidéo pourraient avoir un impact sur la productivité de votre entreprise ?

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