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  • Windows RPC vs XML-RPC

    - by Y.Z
    Is there any benchmark about encoding/decoding certain common typed data in Microsoft RPC NDR engine (DCE 1.1) in comparison with that in XML-RPC-C/C++ in the de-facto C/C++ implementation in XML-RPC? Actually I have to choose between Windows RPC and XML-RPC-C/C++ to implement my own common object infrastructure for High Performance Computing on Windows. Any recommandation about which with regard to their performance? Thank you. Best Regards, Yang

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  • auto updating software on cloud.

    - by iamgopal
    I know wordpress,joomla,drupal etc ( most of php_mysql stack ) can auto detect update in software itself or/and plugin and either ask for user permission to update or auto update it. How to do similar thing on google app engine like cloud computing ? I am creating an open source software which is targeted towards non-computer people. who can not clone my code and update their application easily. what is the easier way to do this ?

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  • Can computer clusters be used for general everyday applications?

    - by Matt Pascoe
    Does anyone know how a computer cluster can be used for everyday applications, like for example video games? I would like to build a computer cluster that can run applications over the cluster that were not specifically designed for computer clusters and still see the performance increase. One use would be for video games, but I would also like to utilize the increased computing power for running a large network of virtualized machines.

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  • SqlBulkCopy is slow, doesn't utilize full network speed

    - by Alex
    Hi, for that past couple of weeks I have been creating generic script that is able to copy databases. The goal is to be able to specify any database on some server and copy it to some other location, and it should only copy the specified content. The exact content to be copied over is specified in a configuration file. This script is going to be used on some 10 different databases and run weekly. And in the end we are copying only about 3%-20% of databases which are as large as 500GB. I have been using the SMO assemblies to achieve this. This is my first time working with SMO and it took a while to create generic way to copy the schema objects, filegroups ...etc. (Actually helped find some bad stored procs). Overall I have a working script which is lacking on performance (and at times times out) and was hoping you guys would be able to help. When executing the WriteToServer command to copy large amount of data ( 6GB) it reaches my timeout period of 1hr. Here is the core code for copying table data. The script is written in PowerShell. $query = ("SELECT * FROM $selectedTable " + $global:selectiveTables.Get_Item($selectedTable)).Trim() Write-LogOutput "Copying $selectedTable : '$query'" $cmd = New-Object Data.SqlClient.SqlCommand -argumentList $query, $source $cmd.CommandTimeout = 120; $bulkData = ([Data.SqlClient.SqlBulkCopy]$destination) $bulkData.DestinationTableName = $selectedTable; $bulkData.BulkCopyTimeout = $global:tableCopyDataTimeout # = 3600 $reader = $cmd.ExecuteReader(); $bulkData.WriteToServer($reader); # Takes forever here on large tables The source and target databases are located on different servers so I kept track of the network speed as well. The network utilization never went over 1% which was quite surprising to me. But when I just transfer some large files between the servers, the network utilization spikes up to 10%. I have tried setting the $bulkData.BatchSize to 5000 but nothing really changed. Increasing the BulkCopyTimeout to an even greater amount would only solve the timeout. I really would like to know why the network is not being used fully. Anyone else had this problem? Any suggestions on networking or bulk copy will be appreciated. And please let me know if you need more information. Thanks. UPDATE I have tweaked several options that increase the performance of SqlBulkCopy, such as setting the transaction logging to simple and providing a table lock to SqlBulkCopy instead of the default row lock. Also some tables are better optimized for certain batch sizes. Overall, the duration of the copy was decreased by some 15%. And what we will do is execute the copy of each database simultaneously on different servers. But I am still having a timeout issue when copying one of the databases. When copying one of the larger databases, there is a table for which I consistently get the following exception: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. It is thrown about 16 after it starts copying the table which is no where near my BulkCopyTimeout. Even though I get the exception that table is fully copied in the end. Also, if I truncate that table and restart my process for that table only, the tables is copied over without any issues. But going through the process of copying that entire database fails always for that one table. I have tried executing the entire process and reseting the connection before copying that faulty table, but it still errored out. My SqlBulkCopy and Reader are closed after each table. Any suggestions as to what else could be causing the script to fail at the point each time?

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  • how to speed up the code??

    - by kaushik
    i have very huge code about 600 lines plus. cant post the whole thing here. but a particular code snippet is taking so much time,leading to problems. here i post that part of code please tell me what to do speed up the processing.. please suggest the part which may be the reason and measure to improve them if this small part of code is understandable. using_data={} def join_cost(a , b): global using_data #print a #print b save_a=[] save_b=[] print 1 #for i in range(len(m)): #if str(m[i][0])==str(a): save_a=database_index[a] #for i in range(len(m)): # if str(m[i][0])==str(b): #print 'save_a',save_a #print 'save_b',save_b print 2 save_b=database_index[b] using_data[save_a[0]]=save_a s=str(save_a[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') print 3 for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) end_time=save_a[4] #print end_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(end_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 q=[] print 4 l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') q=k3.split(' ') #print q print 5 s=str(save_b[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) strt_time=save_b[3] #print strt_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(strt_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 w=[] l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') w=k3.split(' ') #print w cost=0 for i in range(12): #print q[i] #print w[i] h=float(q[i])-float(w[i]) cost=cost+math.pow(h,2) j_cost=math.sqrt(cost) #print cost return j_cost def target_cost(a , b): a=(b+1)*3 b=(a+1)*2 t_cost=(a+b)*5/2 return t_cost r1='shht:ra_77' r2='grx_18' g=[] nodes=[] nodes=nodes+[[r1]] for i in range(len(y_in_db_format)): g=y_in_db_format[i] #print g #print g[0] g.remove(str(g[0])) nodes=nodes+[g] nodes=nodes+[[r2]] print nodes print "lenght of nodes",len(nodes) lists=[] #lists=lists+[r1] for i in range(len(nodes)): for j in range(len(nodes[i])): lists=lists+[nodes[i][j]] #lists=lists+[r2] print lists distance={} for i in range(len(lists)): if i==0: distance[str(lists[i])]=0 else: distance[str(lists[i])]=long(123231223) #print distance group_dist=[] infinity=long(123232323) for i in range(len(nodes)): distances=[] for j in range(len(nodes[i])): #distances=[] if i==0: distances=distances+[[nodes[i][j], 0]] else: distances=distances+[[nodes[i][j],infinity]] group_dist=group_dist+[distances] #print distances print "group_distances",group_dist #print "check",group_dist[0][0][1] #costs={} #for i in range(len(lists)): #if i==0: # costs[str(lists[i])]=1 #else: # costs[str(lists[i])]=get_selfcost(lists[i]) path=[] for i in range(len(nodes)): mini=[] if i!=(len(nodes)-1): #temp=long(123234324) #Now calculate the cost between the current node and each of its neighbour for k in range(len(nodes[(i+1)])): for j in range(len(nodes[i])): current=nodes[i][j] #print "current_node",current j_distance=join_cost( current , nodes[i+1][k]) #t_distance=target_cost( current , nodes[i+1][k]) t_distance=34 #print distance #print "distance between current and neighbours",distance total_distance=(.5*(float(group_dist[i][j][1])+float(j_distance))+.5*(float(t_distance))) #print "total distance between the intial_nodes and current neighbour",total_distance if int(group_dist[i+1][k][1]) > int(total_distance): group_dist[i+1][k][1]=total_distance #print "updated distance",group_dist[i+1][k][1] a=current #print "the neighbour",nodes[i+1][k],"updated the value",a mini=mini+[[str(nodes[i+1][k]),a]] print mini

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  • Books and resources for Java Performance tuning - when working with databases, huge lists

    - by Arvind
    Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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  • heartbeat: Bad nodename in /etc/ha.d//haresources [node1]

    - by Richard
    I'm trying to start heartbeat on Ubuntu 10.04 with service heartbeat start, but getting the following errors: heartbeat[24829]: 2011/11/22_19:31:07 ERROR: Bad nodename in /etc/ha.d//haresources [node1] heartbeat[24829]: 2011/11/22_19:31:07 ERROR: Configuration error, heartbeat not started. On on server uname -n produces loadb1, on the second server uname -n produces loadb2. The two servers can ping each other okay with those names. This is /etc/ha.d/ha.cnf on both servers: debugfile /var/log/ha-debug logfile /var/log/ha-log logfacility local0 keepalive 2 deadtime 10 udpport 694 bcast eth1 ucast eth0 my.external.ip ucast eth0 my.external.ip ucast eth1 10.0.0.5 ucast eth1 10.0.0.6 #udp eth0 node loadb1 node loadb2 auto_failback off And this is /etc/ha.d/haresources on both servers: node1 IPaddr::46.20.121.113 httpd smb dhcpd Authkeys is also set up. What am I doing wrong? The part where I'm least clear is the ucast/bcast lines.

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  • Exchange 2010 DAG Automatic Failover Testing/Issue. Not always automatically failing over to health

    - by Richard
    Ok I've got 2 exchange 2010 servers that run client access/hub transport/mailbox roles and one exchange 2010 server running just client access/hub transport roles and acts as my bridgehead. The two mailbox servers are running one database setup in a DAG. Server A shows the DB Mounted and Server B shows Healthy. If I reboot Server A via windows GUI Server B switches from healthy to mounted and I see hardly any interruption in service using Outlook 2007. Server A shows "Service down", then "Failed" then "Healthy" and leaves the DB mounted on Server B. This is how it should work, so far so good. Now if I test Server A being shut down cold, or unplugging both nics from network to simulate failure, Server B switches from Healthy to Mounted and server A switches to "Service Down" but my outlook client never connects to the DB mounted on server B! I can connect to server C (client access/hub transport) and get to my email and even send new email out, but incoming email doesn't deliver until Server A is brought back online and it's DB goes back to Healthy status. So I don't understand why it auto fail-overs when I reboot the server with the mounted DB copy, causing very little outlook 2007 hiccup if any. But when I shutdown or DC the mounted DB server it DOES mount the healthy copy but outlook 2007 clients can't connect.. I hope the picture I'm trying to paint makes some sense, it's driving me a little batty. Any help would be appreciated!

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  • Unexpected start of already-primary server processes when heartbeat on secondary is stopped.

    - by vorik
    Hi, I've got an active-passive Heartbeat cluster with Apache, MySQL, ActiveMQ and DRBD. Today, I wanted to perform hardware-maintenance on the secondary node (node04), so I stopped the heartbeat service before shutting it down. Then, the primary node (node03) received a shutdown notice from the secondary node (node04). This logging comes from the primary node: node03 heartbeat[4458]: 2010/03/08_08:52:56 info: Received shutdown notice from 'node04.companydomain.nl'. heartbeat[4458]: 2010/03/08_08:52:56 info: Resources being acquired from node04.companydomain.nl. harc[27522]: 2010/03/08_08:52:56 info: Running /etc/ha.d/rc.d/status status heartbeat[27523]: 2010/03/08_08:52:56 info: Local Resource acquisition completed. mach_down[27567]: 2010/03/08_08:52:56 info: /usr/share/heartbeat/mach_down: nice_failback: foreign resources acquired mach_down[27567]: 2010/03/08_08:52:56 info: mach_down takeover complete for node node04.companydomain.nl. heartbeat[4458]: 2010/03/08_08:52:56 info: mach_down takeover complete. harc[27620]: 2010/03/08_08:52:56 info: Running /etc/ha.d/rc.d/ip-request-resp ip-request-resp ip-request-resp[27620]: 2010/03/08_08:52:56 received ip-request-resp drbddisk OK yes ResourceManager[27645]: 2010/03/08_08:52:56 info: Acquiring resource group: node03.companydomain.nl drbddisk Filesystem::/dev/drbd0::/data::ext3 mysql apache::/etc/httpd/conf/httpd.conf LVSSyncDaemonSwap::master monitor activemq tivoli-cluster MailTo::[email protected]::DRBDFailureDrisAcc MailTo::[email protected]::DRBDFailureDrisAcc 1.2.3.212 ResourceManager[27645]: 2010/03/08_08:52:56 info: Running /etc/ha.d/resource.d/drbddisk start Filesystem[27700]: 2010/03/08_08:52:57 INFO: Running OK ResourceManager[27645]: 2010/03/08_08:52:57 info: Running /etc/ha.d/resource.d/mysql start mysql[27783]: 2010/03/08_08:52:57 Starting MySQL[ OK ] apache[27853]: 2010/03/08_08:52:57 INFO: Running OK ResourceManager[27645]: 2010/03/08_08:52:57 info: Running /etc/ha.d/resource.d/monitor start monitor[28160]: 2010/03/08_08:52:58 ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/activemq start activemq[28210]: 2010/03/08_08:52:58 Starting ActiveMQ Broker... ActiveMQ Broker is already running. ResourceManager[27645]: 2010/03/08_08:52:58 ERROR: Return code 1 from /etc/ha.d/resource.d/activemq ResourceManager[27645]: 2010/03/08_08:52:58 CRIT: Giving up resources due to failure of activemq ResourceManager[27645]: 2010/03/08_08:52:58 info: Releasing resource group: node03.companydomain.nl drbddisk Filesystem::/dev/drbd0::/data::ext3 mysql apache::/etc/httpd/conf/httpd.conf LVSSyncDaemonSwap::master monitor activemq tivoli-cluster MailTo::[email protected]::DRBDFailureDrisAcc MailTo::[email protected]::DRBDFailureDrisAcc 1.2.3.212 ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/IPaddr 1.2.3.212 stop IPaddr[28329]: 2010/03/08_08:52:58 INFO: ifconfig eth0:0 down IPaddr[28312]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/MailTo [email protected] DRBDFailureDrisAcc stop MailTo[28378]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/MailTo [email protected] DRBDFailureDrisAcc stop MailTo[28433]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/tivoli-cluster stop ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/activemq stop activemq[28503]: 2010/03/08_08:53:01 Stopping ActiveMQ Broker... Stopped ActiveMQ Broker. ResourceManager[27645]: 2010/03/08_08:53:01 info: Running /etc/ha.d/resource.d/monitor stop monitor[28681]: 2010/03/08_08:53:01 ResourceManager[27645]: 2010/03/08_08:53:01 info: Running /etc/ha.d/resource.d/LVSSyncDaemonSwap master stop LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncmaster down LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncbackup up LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncmaster released ResourceManager[27645]: 2010/03/08_08:53:02 info: Running /etc/ha.d/resource.d/apache /etc/httpd/conf/httpd.conf stop apache[28782]: 2010/03/08_08:53:03 INFO: Killing apache PID 18390 apache[28782]: 2010/03/08_08:53:03 INFO: apache stopped. apache[28771]: 2010/03/08_08:53:03 INFO: Success ResourceManager[27645]: 2010/03/08_08:53:03 info: Running /etc/ha.d/resource.d/mysql stop mysql[28851]: 2010/03/08_08:53:24 Shutting down MySQL.....................[ OK ] ResourceManager[27645]: 2010/03/08_08:53:24 info: Running /etc/ha.d/resource.d/Filesystem /dev/drbd0 /data ext3 stop Filesystem[29010]: 2010/03/08_08:53:25 INFO: Running stop for /dev/drbd0 on /data Filesystem[29010]: 2010/03/08_08:53:25 INFO: Trying to unmount /data Filesystem[29010]: 2010/03/08_08:53:25 ERROR: Couldn't unmount /data; trying cleanup with SIGTERM Filesystem[29010]: 2010/03/08_08:53:25 INFO: Some processes on /data were signalled Filesystem[29010]: 2010/03/08_08:53:27 INFO: unmounted /data successfully Filesystem[28999]: 2010/03/08_08:53:27 INFO: Success ResourceManager[27645]: 2010/03/08_08:53:27 info: Running /etc/ha.d/resource.d/drbddisk stop heartbeat[4458]: 2010/03/08_08:53:29 WARN: node node04.companydomain.nl: is dead heartbeat[4458]: 2010/03/08_08:53:29 info: Dead node node04.companydomain.nl gave up resources. heartbeat[4458]: 2010/03/08_08:53:29 info: Link node04.companydomain.nl:eth0 dead. heartbeat[4458]: 2010/03/08_08:53:29 info: Link node04.companydomain.nl:eth1 dead. hb_standby[29193]: 2010/03/08_08:53:57 Going standby [foreign]. heartbeat[4458]: 2010/03/08_08:53:57 info: node03.companydomain.nl wants to go standby [foreign] Soo... What just happened here??? Heartbeat on node04 stopped and told node03, which was the active node at the time. Somehow, node03 decided to start the cluster processes that were already running. (For the processes that are not critical, I always return a 0 from the startupscript so it does not stops the entire cluster when a non-essential part fails.) When starting ActiveMQ, it returns status 1 because it is already running. This fails the node and shuts everything down. As heartbeat is not running on the secondary node, it cannot failover to there. When I tried to run ha_takeover to restart the resources, absolutely nothing happened. Only after I restarted heartbeat on the primary node the resources could be started (after a delay of 2 minutes). These are my questions: Why does heartbeat on the primary node try to start the cluster processes again? Why did ha_takeover not work? What can I do to prevent this from happening? Server configuration: DRBD: version: 8.3.7 (api:88/proto:86-91) GIT-hash: ea9e28dbff98e331a62bcbcc63a6135808fe2917 build by [email protected], 2010-01-20 09:14:48 0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate B r---- ns:0 nr:6459432 dw:6459432 dr:0 al:0 bm:301 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:0 uname -a Linux node04 2.6.18-164.11.1.el5 #1 SMP Wed Jan 6 13:26:04 EST 2010 x86_64 x86_64 x86_64 GNU/Linux haresources node03.companydomain.nl \ drbddisk \ Filesystem::/dev/drbd0::/data::ext3 \ mysql \ apache::/etc/httpd/conf/httpd.conf \ LVSSyncDaemonSwap::master \ monitor \ activemq \ tivoli-cluster \ MailTo::[email protected]::DRBDFailureDrisAcc \ MailTo::[email protected]::DRBDFailureDrisAcc \ 1.2.3.212 ha.cf debugfile /var/log/ha-debug logfile /var/log/ha-log keepalive 500ms deadtime 30 warntime 10 initdead 120 udpport 694 mcast eth0 225.0.0.3 694 1 0 mcast eth1 225.0.0.4 694 1 0 auto_failback off node node03.companydomain.nl node node04.companydomain.nl respawn hacluster /usr/lib64/heartbeat/dopd apiauth dopd gid=haclient uid=hacluster Thank you very much in advance, Ger Apeldoorn

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  • Managing scalability and availability with two servers running Apache Httpd, Apache Mina and MySQL

    - by celalo
    Hello, I am not a developer and I don't much experience with scalable server architectures. But I am in need of a highly available and scalable system for one of my projects. There is going to be two servers I am going to use for the time being. Both with 4 core CPUs and 8 GB RAM with RAID structures running CentOS 5.4. I will also have feature called "Failover IP" which enables to direct an IP address to another server within short time. The applications which will be run on the servers: There is going to be a Java application based on Apache Mina server for handling TCP requests from some hundreds of network devices where the devices are going to send request as much as one request per minute. Handling those requests, includes parsing the requests and inserting a few rows to the Database. Parsing requests before inserting data to the DB does take neglectable time. There is going to be MySQL server, as I stated above. Also there is going to be a PHP web application running on Apache Httpd Server which uses the same DB with the Java application. What I wish to have is to make use of those two servers at the most. I was imagining to have the servers identical, sharing the work load. MySQL could be a cluster maybe? And if some application fails or the whole machine goes down, the other will continue serving the requests seamlessly. Reminding that a "Failover IP" feature will be available for me to take advantage of. Also, It should be kept in mind that number of servers could increase in time, to meet the demand. What can you suggest? Which kind of tools I can make use of? Which kind of monitoring software (paid/unpaid) I have? Thanks in advance.

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  • Choice of operating systems for a Rackspace cloud installation

    - by riteshmnayak
    I am planning to use Rackspace cloud services to host a java web application and also run apace for wordpress and trac. What would be a stable operating system to host such an application. My requirements are that the core OS bundle should be minimalistic (so I can install only what I want), consume very little memory and be performant. I would also need it to contain softwares for the common lamp stack, J2EE stack etc. A supported package manager would be lovely. My choices are listed below. RHEL 5.3 or 5.4 Debian Lenny Ubuntu 8.04 onwards Centos 5.3 or 5.4 Arch 2009.02 Gentoo 2008.0 or 10.1 Fedora 11 or 12 PS: can somebody add the rackspace tag to this? Edit to remove this line as well. Thanks

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  • ACPI Throttling in Ubuntu

    - by Evan
    I'm looking to throttle my cpu through the ACPI. I've read up on it, but I keep receiving permission denied statements. I have 8 available throttling states. Here are the outcomes of my atttempts: evan@evan-laptop:/proc/acpi/processor/CPU0$ echo 3 /proc/acpi/processor/CPU0/throttling bash: /proc/acpi/processor/CPU0/throttling: Permission denied evan@evan-laptop:/proc/acpi/processor/CPU0$ sudo echo 3 /proc/acpi/processor/CPU0/throttling bash: /proc/acpi/processor/CPU0/throttling: Permission denied EDIT: For reference, I am running Ubuntu Karmic with Intel Core Duo T2500 with ACPI enabled

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  • Avoiding DNS timeouts when a dns server fails

    - by user65124
    Hi there. We have a small datacenter with about a hundred hosts pointing to 3 internal dns servers (bind 9). Our problem comes when one of the internal dns servers becomes unavailable. At that point all the clients that point to that server start performing very slowly. The problem seems to be that the stock linux resolver doesn't really have the concept of "failing over" to a different dns server. You can adjust the timeout and number of retries it uses, (and set rotate so it will work through the list), but no matter what settings one uses our services perform much more slowly if a primary dns server becomes unavailable. At the moment this is one of the largest sources of service disruptions for us. My ideal answer would be something like "RTFM: tweak /etc/resolv.conf like this...", but if that's an option I haven't seen it. I was wondering how other folks handled this issue? I can see 3 possible types of solutions: Use linux-ha/Pacemaker and failover ips (so the dns IP VIPs are "always" available). Alas, we don't have a good fencing infrastructure, and without fencing pacemaker doesn't work very well (in my experience Pacemaker lowers availability without fencing). Run a local dns server on each node, and have resolv.conf point to localhost. This would work, but it would give us a lot more services to monitor and manage. Run a local cache on each node. Folks seem to consider nscd "broken", but dnrd seems to have the right feature set: it marks dns servers as up or down, and won't use 'down' dns servers. Any-casting seems to work only at the ip routing level, and depends on route updates for server failure. Multi-casting seemed like it would be a perfect answer, but bind does not support broadcasting or multi-casting, and the docs I could find seem to suggest that multicast dns is more aimed at service discovery and auto-configuration rather than regular dns resolving. Am I missing an obvious solution?

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  • What is the difference between Anycast and GeoDNS / GeoIP wrt HA?

    - by Riyad
    Based on the Wikipedia description of Anycast, it includes both the distribution of a domain-name-to-many-IP-mapping across many DNS servers as well as replying to clients with the most geographically close (or fastest) server. In the context of a globally distributed, highly available site like google.com (or any CDN service with many global edge locations) this sounds like the two key features one would need. DNS services like Amazon's Route53, EasyDNS and DNSMadeEasy all advertise themselves as Anycast-enabled networks. Therefore my assumption is that each of these DNS services transparently offer me those two killer features: multi-IP-to-domain mapping AND routing clients to the closest node. However, each of these services seem to separate out these two functionalities, referring to the 2nd one (routing clients to closest node) as "GeoDNS", "GeoIP" or "Global Traffic Director" and charge extra for the service. If a core tenant of an Anycast-capable system is to already do this, why is this functionality being earmarked as this extra feature? What is this "GeoDNS" feature doing that a standard Anycast DNS service won't do (according to the definition of Anycast from Wikipedia -- I understand what is being advertised, just not why it isn't implied already). I get extra-confused when a DNS service like Route53 that doesn't support this nebulous "GeoDNS" feature lists functionality like: Fast – Using a global anycast network of DNS servers around the world, Route 53 is designed to automatically route your users to the optimal location depending on network conditions. As a result, the service offers low query latency for your end users, as well as low update latency for your DNS record management needs. ... which sounds exactly like what GeoDNS is intended to do, but geographically directing clients is something they explicitly don't support it yet. Ultimately I am looking for the two following features from a DNS provider: Map multiple IP addresses to a single domain name (like google.com, amazon.com, etc. does) Utilize a DNS service that will respond to client requests for that domain with the IP address of the nearest server to the requestee. As mentioned, it seems like this is all part of an "Anycast" DNS service (all of which these services are), but the features and marketing I see from them suggest otherwise, making me think I need to learn a bit more about how DNS works before making a deployment choice. Thanks in advance for any clarifications.

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  • Which Linux is the most efficient?

    - by quandary
    Simple question: There is a gazillion Linux distributions out there. Which one (distribution/incl. window manager) makes (technically) the most efficient use of my (aging) computer ? I have appx. 1 GB RAM and a 1.6 GHz processor, 120 GB hd. I develop applications (C++/.NET/mono/ASP/PostGre SQL/). Usually, I prefer distros with apt-get. Anybody knows which one takes the most care of my limited RAM, and wich one is the fastest/slimmest of them all, that has a decent repo and is damn fast)

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  • Bluray Drives: 2x vs 4x vs 6x vs 8x read/writespeed.

    - by Wesley
    Hi all, I couldn't find a duplicate question, but I was wondering what the differences are between different read/write speeds for Bluray drive. I'm planning on buying one for a build but don't know if I can cheap out on getting a Bluray 2x drive or spend more money for a quality Bluray 8x drive. Will I just experience more lag/buffering times for Bluray discs on a 2x and none for a 6x or 8x? Thanks in advance.

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  • HAProxy -- pause/queue all traffic without losing requests

    - by Marc
    I basically have the same problem as mentioned in this thread -- I would like to temporarily suspend all requests to all servers of a certain backend, so that I can upgrade the backend and the database it uses. Since this is a live system, I would like to queue up requests, and send them to the backend servers once they've been upgraded. Since I'm doing a database upgrade with the code change, I have to upgrade all backend servers simultaneously, so I can't just bring one down at a time. I tried using the tcp-request options combined with removing the static healthcheck file as mentioned in that thread, but had no luck. Setting the default "maxconn" value to 0 seems to pause and queue connections as desired, but then there seems to be no way to increase the value back to a positive number without restarting HAProxy, which kills all requests that had been queued up until that point. (The "hot-reconfiguration" options using -sf and -st start a new process, which doesn't seem to do what I want). Is what I'm trying to do possible?

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  • NFS v4, HA Migration, and stale handles on clients

    - by Karl Katzke
    I'm managing a server running NFS v4 with Pacemaker/OpenAIS. NFS is configured to use TCP. When I migrate the NFS server to another node in the Pacemaker cluster, even though the metadata is persisted, connections from the clients 'hang' and eventually time out after 90 seconds. After that 90 seconds, the old mountpoint becomes 'stale' and the mounted files can no longer be accessed. The 90 second grace period seems to be part of the server configuration and not the client configuration. I see this message on the server: kernel: NFSD: starting 90-second grace period If I restart the NFS client on the client nodes after I migrate (unmounting and then remounting the share), then I don't experience the problem, but connections and file transfers still interrupted. Three questions: What is the 90 second grace period? What's it there for? How can I keep the files from going stale on the clients without restarting them after I migrate the NFS server to another node? Is it actually possible to migrate the NFS server without having large file uploads drop?

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  • Mac Management and Security

    - by Bart Silverstrim
    I was going through some literature on managing OS X laptops and asked someone some questions about usage scenarios when using the MacBooks. I asked someone more knowledgeable than I about whether it was possible for my Mac to be taken over if I were visiting another site for a conference or if I went on a wifi network at a local coffee house with policies from an OS X Server with workgroup manager (either legit for the site or someone running a version of OS X Server on hardware they have hidden somewhere on the network), which apparently could be set up to do things like limit my access to Finder or impose other neat whiz-bang management features. He said that it is indeed possible for it to happen as it would be assigned via the DHCP server and the OS X server would assume my Mac is a guest and could hand out restrictions and apparently my Mac will happily accept them without notifying me or giving me an option, unlike Windows which I believe would need to be joined to a domain before it becomes "managed" by Active Directory. So my question is as network admins and sysadmins with users traveling with MacBooks, is there a way to reasonably protect your users from having their machines hijacked without resorting to just turning off networking all the time? Or isn't this much of a security hazard? What threat does this pose to the road warriors in your businesses?

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