Networking :: Practive For Implementation Of A Failover Server?
Jan 20, 2011
I'm in need of some advise from you guys. I'm currently running a live production serverA, and last week it went down for a couple of hours which was really bad to say the least.
I've been thinking about building a mirror serverB that will rsync my data nightly. Now I don't want to load balance here, I just need to be able to switch to serverB when serverA goes down for any reason.
Would the best solution for this is to change my main nameserver entry when I want to switch ? I'm just curious if it will be a few hours or an instant change.
I thought I'd ask before attempting this live.
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Feb 14, 2010
What is the current state of NFS failover (i.e. setting up two server with shared storage, with automatic failover if one fails?) I've seen a cookbook, but no details that would let me assess how well it works. There are lots of complex issues with data consistency, but the detailed information on that is years old. Our needs are fairly simple: 2 servers, a shared array, and I'm reasonably sure that we don't use locking. However we'd like failover to work reliably without loss of data.
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Apr 23, 2010
I am familiar with active to active cluster failover and active to pasive failover, but what is network failover?
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Feb 9, 2011
I am using Centos. I have read places that you can use Drbd + heartbeat + nfs to make a simple failover NFS server.I can't find any document that works though. I've tried 20 or so, including some Debian ones.So, does anyone have any other ideas of how to do this?Point me in the right direction please.I want 2 nodes. One to be actively serving an NFS share The other to be ready for failover. If the first one goes out, the second takes over.Meaning, the filesystem is in sync, the IP must change, and NFS must come up
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Jun 8, 2010
We are having a production setup where we are having one SAN storage and two RHEL machines. Now we have created a SAN LUN, say for example trylun. Now we have mounted the same SAN partition on both the machines of RHEL on the same mountpoint path say for example /trylun. After that we have installed RHEL Cluster suite to create a failover cluster.
Now we will be having one Ingres Database service for which data will be stored in SAN storage LUN mounted on both the machine say for example /trylun. When service on one machine will be down then RHEL Cluster Suite failover cluster will takeover and then it will start the same service on another node and handle the failover. Wether Ingres will run from node 1 or node 2 will not make any difference as both are using shared SAN storage i.e /trylun in our example. So same data storage will be used by both the ingres service on both the servers.
Now I have to simulate the same in my office test environment. But the problem is, in office test environment I will not have SAN server as it is additional cost. And I will have fedora operating system.
So I wanted to know is how can we create a shared file system like SAN in fedora (Is NFS a solution). And after creating the shared file system how can we create a failover cluster in fedora if we do not have Red Hat Cluster Suite.
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Feb 15, 2011
My question is about setting up SMB and AFP failover between two servers. The plan is to have two servers both running CentOS with one acting as a primary node and one as secondary failover node. I have never set anything like this up before. In the past I have always worked with SAN's primary XSAN/StorNext. Both of which handle failover pretty much automatically. Unfortunately there isn't the budget on this job to install a SAN. Also this is only for temporary use for a week in a production office.
My thoughts where to run the two servers and use rsync on a cron tab to keep the data synchronised between the two. In an ideal world clients would log on to the primary and if that fails, seamlessly moved over to the secondary. I'm guessing however this is not possible outside of a SAN environment. So keeping the two servers synced and the clients manually moving over to the secondary manually is, I'm guessing, my only real option.
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May 6, 2010
IPtables, implementing each type of NAT
-Full Cone NAT
-Restricted Cone NAT
-Port Restricted Cone NAT
-Symmetric NAT
using IPTables.
Explanation:
Full Cone: A full cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Furthermore, any external host can send a packet to the internal host, by sending a packet to the mapped external address.
Restricted Cone: A restricted cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Unlike a full cone NAT, an external host (with IP address X) can send a packet to the internal host only if the internal host had previously sent a packet to IP address X.
Port Restricted Cone: A port restricted cone NAT is like a restricted cone NAT, but the restriction includes port numbers. Specifically, an external host can send a packet, with source IP address X and source port P, to the internal host only if the internal host had previously sent a packet to IP address X and port P.
Symmetric: A symmetric NAT is one where all requests from the same internal IP address and port, to a specific destination IP address and port, are mapped to the same external IP address and port. If the same host sends a packet with the same source address and port, but to a different destination, a different mapping is used. Furthermore, only the external host that receives a packet can send a UDP packet back to the internal host.
On the netfilter mailinglist, Pedro Goncalves suggested the following:
192.168.2.170 is "public" address and 10.0.0.1 is "private" address
/-"Full Cone NAT", with the following rules:/
HTML Code:
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 192.168.2.170
iptables -t nat -A PREROUTING -i eth0 -j DNAT --to-destination 10.0.0.1
/-"Port Restricted Cone NAT", with just a single rule:/
HTML Code:
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 192.168.2.170
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Apr 10, 2009
How to implement Network Protocols.
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Dec 9, 2010
Have any of the below TCP based applications are implemented over SCTP in Linux ?
1. ftp
2. telnet
3. HTTP
Or any other applications ?
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Nov 11, 2010
I have a dual-homed Debian server running squid, but not acting as a router. Simplied network diagram is below - there are other local hops between the gateways and the Internet.
Code:
(eth0 @ 192.168.44.2) <--> (Gateway1 @ 192.168.44.1) <--> Internet
(eth1 @ 192.168.55.2) <--> (Gateway2 @ 192.168.55.1) <--> Internet
Using Gateway1 gives a very fast, but not always reliable route to the Internet. Using Gateway2 gives a slower, but more reliable route to the Internet. The server uses Gateway1 as the default gateway.
I have written a script that pings three hosts on the Internet, and if all three are down, switches the default gateway to Gateway2. This part seems to be easy, but I'd like know if there is a way of routing a ICMP/ping out eth0 to a host, with all other traffic to the host going out eth1, so I can determine if the Internet is reachable via Gateway1 again.
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Nov 30, 2010
My friend has a server with 2 ips, 1 primary and 1 secondary/failover. He has given me a shell account and I want to use ssh to route my home http traffic through it like a socks proxy. I connect to his server using the secondary ip like this:
ssh me@secondary_ip -p port -D forwarding_port
It builds a proxy, however it uses the primary ip of the server, not the secondary ip that I logged in with. When using irssi I've bound it to the secondary ip with no problem. If I try to use the -b flag I get the error: cannot bind: Cannot assign requested address.
how I can bind the ssh tunnel to the secondary ip?
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Jul 3, 2011
I've configuration like this :
Quote:
I try to configure my /etc/rc.local with these setting :
Quote:
But whenever i check my router after reboot, still i can't connect to inet.
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Jul 7, 2011
We run redundant switches that two nic's on each server connect to. We also run bonding on our servers. Because we have two switches, we can't run lacp or anything. If a switch goes into a crashed state where it doesn't pass traffic but still provides link, bonding thinks the interface is still up and thus will still send traffic through it. Does anybody know a better way to configure the fail over of the interface? This would be a similar situation to somebody using a media converter.
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Oct 27, 2010
I don't have much experience in clustering. And I'm deploying a cluster system on CentOS.But I don't know how long a node failover and another node take over those resouces to continue running service is good, fast or slow? 1s, 10s or
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Mar 1, 2011
I am familiar with windows 2008 cluster servers, and I just started testing with centos cluster. I am creating a simple 2-node cluster, for a simple ping test.
Node 1: 10.0.0.1
Node 2: 10.0.0.1
Virtual ip: 10.0.0.10
So far, I can ping a virtual ip, and manually relocate it between the nodes, but I didn't figure out, how to do this automatically. So this is my question: How can I setup the cluster, to it automatically failover the a service to another node case one node fails?
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Feb 5, 2011
not able to solve an error when i try to do a wireless scenario in ns2.
num_nodes is set 3
warning: Please use -channel as shown in tcl/ex/wireless-mitf.tcl
INITIALIZE THE LIST xListHead
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Aug 2, 2010
Can I know the implemention of RSA(Encryption and decryption) algorithm in C / C++.
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Apr 27, 2011
I have a copy of the MD5 algorithm and I'm taking a look at the source. It's pretty interesting but there are a few things that I'm curious about and I was wondering if anyone a bit more intuitive than I could help me out.The function declarations in the MD5 files are a bit unfamiliar to me. There is a macro used called PROTO_LIST, which I'm still not sure as to what this thing is doing exactly, but it's littered everywhere throughout the source.The signature here isn't too unfamiliar to me with the exception of the position of the PROTO_LIST macro. So here is a function with an unnamed argument of type MD5_CTX*.To me, this resembles an initializer list found in C++ with constructors but I certainly don't think that is the case here. So my questions about this are (1) how is this legal code in C and (2) what functionality has the PROTO_LIST macro provided for the function?
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Sep 30, 2010
We have setup a High Available Cluster on two RHEL 5.4 machines with Redhat Cluster Suite (RHCS) having following configuration.
1. Both machines have Mysql server, Apache web server and Zabbix server.
2. Mysql database and web pages reside in SAN.
3. Active machine holds virtual IP and mounted shared disk.
4. We have also included a script in RHCS which takes care of starting Mysql, Apache and zabbix server on the machine which turns active when cluster switches over.
The above configuration holds good if Active machine goes down as a result of hardware failure or Reboot. What if, If any one service say Apache/Mysql/zabbix running on active hangs or become unresponsive.How can we handle this scenario ? Please advice.
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Jan 3, 2010
I currently have 9 physical servers that I wanted to condense to 1 physical server with 7 VMs using Xen. The only issue that I have with doing this is that if the server happens to fail due to hardware problems, I am going to have a major issue. I wanted to set up a two node cluster so in the event of something happening to one of the servers, it will automatic failover to the next.
With so many ways to cluster servers, does anyone have any suggestions on the way to perform my needed task. The OS for Xen will be Red Hat and the VMs will have many versions of linux. Some of the VMs will have mysql, apache, dns, and postfix running.
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May 11, 2010
i have done everything that all the documentations have said and i still cant get this bloody thing working. some one give me the exact commands that removes all traces of all wine packages. and then can someone give me the exact commands to install.
which user i must be doing this under and exactly what i must configure in the config files. all that i want too accomplish by this is to successfully play games on my pc.
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Oct 20, 2010
I am trying to understand the implementation of iptables and netfilters. Any good links or docs.
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Feb 25, 2010
I need to optimize the implementation of DSR algo using NS-2. Now i need to identify the first of all "the parameters which i can change and which are effective in optimization point of view." I want to get into the c++ code as well as header files which are used to implement DSR algo.
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Aug 11, 2011
I am trying to find a leach protocol implementation for ns2.34 but all links available are dealing with ns2.27 Are the instructions valid for ns2.34?
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Dec 7, 2010
I'm looking for linear hashing implementation in C language. PS: I have to implement this on Ubuntu 10.04 Linux on 64 bit machine.
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Apr 6, 2011
I've implemented a program URL... which reads digital IF data from a radio receiver through a named pipe, measures power levels, and sends the result to stdout. The program is interactive; there is a thread that reads from stdin to watch for commands, a thread that constantly either reads data from the named pipe or throws data away, and an array of processing threads. The program uses GTK+extra to plot the signals. The IF data stream bandwidth exists at the limits of today's technology (is very very fast).
Problem Statement:The program works fine with a few bugs. I've learned since I've made it that using global state variables to coordinate threads isn't a good way of doing it. I also only had knowledge of mutexes and polled the state variable instead of using other methods.My reimplementation will use the following:
- One "Stdin Command Monitoring" thread
- One "Get data from named pipe" thread
- One post-processor thread
- N Processing threads
All threads are alive during the life of main()There are N buffers. Data will come in from the named pipe, and the "Get data" thread will write the data to an "available" buffer. When the buffer is full it will be marked as "full". There will be N processing threads, one for each buffer. When a processing threads' buffer is full, it will process the buffer and save the result to a final buffer. At the end of a number of averages, the post-processor thread will perform a final process on the final buffer and send the results to stdout.
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Nov 10, 2009
Have been tasked with a couple of Sunfire X2100 that I am slapping Fedora 11 onto for some high profile tasks around the office. Have two drives of the same size in each server and would like to have the two disks mirrored for redundancy. Admittedly I am new at Linux administration and am feeling over my head.
1. Can this be managed during the installation process of Fedora 11?
2. If yes, let me know the step by step please.
3. If no, I take it a cron job of rsync is going to be my best option.
4. Alternatives insights etc.
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May 4, 2010
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Jun 9, 2011
I'm Redhat 5 user, and I want to implement Kernel-based Virtual Machine. I tried too much search in google but I cant find the perfect instruction regarding it.
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Mar 19, 2010
Subject of my school work:"Web interface for managing firewall and band on the access server (Linux)"I have a big problem because I do not know how to safely implement the change in the system and show the logs on the Web page.Unfortunately, the number of solutions for today is enormous and it is increasingly difficult to me to decide on the right.They are:
1. Launching a web server with root privileges (the default mode of miniserv'a Webmin)
2. CGI scripts on apache SUID (mode webmin on "foreign" server)
3. suPHP or suexec
4. Cron implements changes to the root
5. Daemon in C "periodically" implement changes in the configuration files created by PHP
6. Daemon in C to implement the changes requested in the configuration files created by PHP
7.Use SSH in PHP and after logging into the root of execution of commands in the configuration files created by PHP (the root password in the DB)
8.Use SSH in PHP and after logging into the root of execution of commands in the configuration files created by PHP (the root password, enter manually)
9. Like the above so that the use of sudo and user rights only to the necessary shell commands
10. Add the user apache in the /etc/sudoers can perform all the necessary applications shell commands
11. Seize the opportunity to command: shell_exec ( `sudo php-f / home /example/script.php`), and /etc/sudoers
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