Search Results

Search found 1419 results on 57 pages for 'availability'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 7/57 | < Previous Page | 3 4 5 6 7 8 9 10 11 12 13 14  | Next Page >

  • Multimaster Keepalived Configuration (Virtual IP with Load Balancing)

    - by Rad Akefirad
    Here are requirements: 1. High Availability 2. Load Balancing First configuration 1. Two linux servers have been configured with one static IP for each: 10.17.243.11, 10.17.243.12 2. Keepalived has been installed and configured with one VRRP instance to provide one virtual IP (10.17.243.10 as VIP, 10.17.243.11 as master and 10.17.243.12 as backup). 3. Everything works fine. The VIP is assigned to the master server (10.17.243.11) as long as it is up and running. As soon as it goes down, the VIP will be assigned to the backup server (10.17.243.12). 4. The problem here is all communication goes to the master server. Second configuration 1. I found active-active configuration for Keepalived which is possible by defining more than one VRRP instance. So that both server have two IPs (real 10.17.243.11 and virtual 10.17.243.10 for server #1 and real 10.17.243.12 and virtual 10.17.243.20 for server #2. 2. Everything works fine. we have two VIPs which are accessible (HA). But all communication coming to each IP still goes to one single machine (either server #1 or #2 depending on the IP). However I found some tricks on the DNS to overcome this limitation. But it's not acceptable in our case. Question: Is there any way to have one virtual IP which is assigned to both servers? By that I mean both servers are handling some part of workload (like the thing we do in web server load balancing)? By using either keepalived or some other tools? Thanks in advance.

    Read the article

  • Keepalived for more than 20 virtual addresses

    - by cvaldemar
    I have set up keepalived on two Debian machines for high availability, but I've run into the maximum number of virtual IP's I can assign to my vrrp_instance. How would I go about configuring and failing over 20+ virtual IP's? This is the, very simple, setup: LB01: 10.200.85.1 LB02: 10.200.85.2 Virtual IPs: 10.200.85.100 - 10.200.85.200 Each machine is also running Apache (later Nginx) binding on the virtual IPs for SSL client certificate termination and proxying to backend webservers. The reason I need so many VIP's is the inability to use VirtualHost on HTTPS. This is my keepalived.conf: vrrp_script chk_apache2 { script "killall -0 apache2" interval 2 weight 2 } vrrp_instance VI_1 { interface eth0 state MASTER virtual_router_id 51 priority 101 virtual_ipaddress { 10.200.85.100 . . all the way to . 10.200.85.200 } An identical configuration is on the BACKUP machine, and it's working fine, but only up to the 20th IP. I have found a HOWTO discussing this problem. Basically, they suggest having just one VIP and routing all traffic "via" this one IP, and "all will be well". Is this a good approach? I'm running pfSense firewalls in front of the machines. Quote from the above link: ip route add $VNET/N via $VIP or route add $VNET netmask w.x.y.z gw $VIP Thanks in advance. EDIT: @David Schwartz said it would make sense to add a route, so I tried adding a static route to the pfSense firewall, but that didn't work as I expected it would. pfSense route: Interface: LAN Destination network: 10.200.85.200/32 (virtual IP) Gateway: 10.200.85.100 (floating virtual IP) Description: Route to VIP .100 I also made sure I had packet forwarding enabled on my hosts: $ cat /etc/sysctl.conf net.ipv4.ip_forward=1 net.ipv4.ip_nonlocal_bind=1 Am I doing this wrong? I also removed all VIPs from the keepalived.conf so it only fails over 10.200.85.100.

    Read the article

  • What are the ways to build a failover cluster?

    - by light
    I have a task where I need to build a failover cluster in two cases: first with servers on Red Hat Enterprise 5.1 and second with SUSE Linux Enterprise 11 SP1. Both cases have SAN. I know there are many ways to build failover cluster, but I can’t find out more, so I need next: The ways to build it? I know only virtualization. Any good book or resource to broad my mind? I’ll be glad to hear any suggestion. Thanks! EDIT #1: failover of servers with bussiness application on it. EDIT #2: will be great to hear summary about solutions with SLES servers? EDIT #3: So if I understand correctly, in my cases the main ways are to use internal solutions or virtualization. So now I have additional questions: Does manufacturer of blades provide some solution? For example HP or IBM. (Without virtualization) Do I need additional server to control "heartbeat" between main and redundant servers? (Virtualization) For example I have several physical servers with VMs. Do I need additional server to control availability of VMs and to move VMs to another physical server in the case their physical server failure? Sorry for my poor English. EDIT #4: Failover of VM or OS on physical server. In both cases will be used SAN , it's not specified, but I think with file system image on it. I started to think that my question is stupid and I need to remake it.

    Read the article

  • availability of Win32_MountPoint and Win32_Volume on Windows XP?

    - by SteveC
    From the MSDN articles I've found -- http://msdn.microsoft.com/en-us/library/aa394515(v=VS.85).aspx -- Win32_Volume and Win32_MountPoint aren't available on Windows XP. However, I'm developing a C# app on Windows XP (64bit), and I can get to those WMI classes just fine. Users of my app will be on Windows XP sp2 with .Net 3.5 sp1. Googling around, I can't determine whether I can count on this or not. Am I successful on my system because of one or more of the following: - windows xp service pack 2? - visual studio 2008 sp1 was installed? - .Net 3.5 sp1? Should I use something other than WMI to get at the volume/mountpoint info? Below is sample code that's working... public static Dictionary<string, NameValueCollection> GetAllVolumeDeviceIDs() { Dictionary<string, NameValueCollection> ret = new Dictionary<string, NameValueCollection>(); // retrieve information from Win32_Volume try { using (ManagementClass volClass = new ManagementClass("Win32_Volume")) { using (ManagementObjectCollection mocVols = volClass.GetInstances()) { // iterate over every volume foreach (ManagementObject moVol in mocVols) { // get the volume's device ID (will be key into our dictionary) string devId = moVol.GetPropertyValue("DeviceID").ToString(); ret.Add(devId, new NameValueCollection()); //Console.WriteLine("Vol: {0}", devId); // for each non-null property on the Volume, add it to our NameValueCollection foreach (PropertyData p in moVol.Properties) { if (p.Value == null) continue; ret[devId].Add(p.Name, p.Value.ToString()); //Console.WriteLine("\t{0}: {1}", p.Name, p.Value); } // find the mountpoints of this volume using (ManagementObjectCollection mocMPs = moVol.GetRelationships("Win32_MountPoint")) { foreach (ManagementObject moMP in mocMPs) { // only care about adding directory // Directory prop will be something like "Win32_Directory.Name=\"C:\\\\\"" string dir = moMP["Directory"].ToString(); // find opening/closing quotes in order to get the substring we want int first = dir.IndexOf('"') + 1; int last = dir.LastIndexOf('"'); string dirSubstr = dir.Substring(first , last - first); // use GetFullPath to normalize/unescape any extra backslashes string fullpath = Path.GetFullPath(dirSubstr); ret[devId].Add(MOUNTPOINT_DIRS_KEY, fullpath); } } } } } } catch (Exception ex) { Console.WriteLine("Problem retrieving Volume information from WMI. {0} - \n{1}",ex.Message,ex.StackTrace); return ret; } return ret; }

    Read the article

  • Model availability inside ActionFilter

    - by Sayed Ibrahim Hashimi
    I have created a new ActionFilter for an ASP.NET MVC application that I'm creating. I have an action which accepts an Http Post and the argument of the action method accepts an object, for which I have created and registered a custom model binder. I noticed that inside the IActionFilter.OnActionExecuting the value for filterContext.Controller.ViewData.Model is always null despite the fact that it looks like the model binder is always invoked before the action filter OnActionExecuting method. In contrast to this inside the IActionFilter.OnActionExecuted method of the same action filter the value for filterContext.Controller.ViewData.Model is not null. Do you guys know if this is by design or a bug? If by design are their any links which describe why this is? Thanks.

    Read the article

  • java distributed cache for low latency, high availability

    - by Shahbaz
    I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

    Read the article

  • CodeIgniter not working on PHP 4 server without .htaccess availability

    - by Rasiel
    Hi All, Basically i developed my app on a localhost wamp server with PHP 5. ON uploading to the actual host i notice that The server is running php 4.4.9 Everytime i upload my .htaccess file, the server removes it completely.. seems to not be allowed When i test out the set all i get is a 404 page not found Any help on how to make it work on this PHP 4 server?

    Read the article

  • Amazon Product Availability

    - by user201140
    Many products on amazon are unavailable but a date is given for when they'll be in stock. I've used AWS and got an XML reply but I can't find the date information anywhere. Is it possible to get this information? Thanks. NOTE: This is what i've got as a request, what should I alter? http://ecs.amazonaws.com/onca/xml?AWSAccessKeyId=MYID&AssociateTag=MYTAG&ItemId=THEITEMID&Operation=ItemLookup&ResponseGroup=Large&ReviewSort=-HelpfulVotes&Service=AWSECommerceService&Signature=MYSIGNATURE&Timestamp=2009-12-04T17%3A35%3A43Z&Version=2009-06-01

    Read the article

  • Serial port data availability problem

    - by harry
    Hello Evryone. I am new to this type of programming..i just want some help...regarding what to do when u need to extract the data from the serial port..and how to check that tha data is available in the serial port..so that no data loss is there....

    Read the article

  • Checking COM Port Availability in C#

    - by Jim Fell
    Hello. My C# application populates a comboBox with the COM ports found on the system. I would like the mark the COM ports that are in use as such. I know that I can use try / catch blocks to attempt to open every COM port, but I was wondering if there is a more graceful way to do this. Perhaps using a WMI query? I am using Microsoft Visual C# 2008 Express Edition (.NET 2.0). Any thoughts or suggestions you may have would be appreciated. Thanks.

    Read the article

  • A monkey could do this better - Access to and availability of private member functions in C++

    - by David
    I am wandering the desert of my brain. I'm trying to write something like the following: class MyClass { // Peripherally Related Stuff public: void TakeAnAction(int oneThing, int anotherThing) { switch(oneThing){ case THING_A: TakeThisActionWith(anotherThing); break; //cases THINGS_NOT_A: }; private: void TakeThisActionWith(int thing) { string outcome = new string; outcome = LookUpOutcome(thing); // Do some stuff based on outcome return; } string LookUpOutcome(int key) { string oc = new string; oc = MyPrivateMap[key]; return oc; } map<int, string> MyPrivateMap; Then in the .cc file where I am actually using these things, while compiling the TakeAnAction section, it [CC, the solaris compiler] throws an an error: 'The function LookUpOutcome must have a prototype' and bombs out. In my header file, I have declared 'string LookUpOutcome(int key);' in the private section of the class. I have tried all sorts of variations. I tried to use 'this' for a little while, and it gave me 'Can only use this in non-static member function.' Sadly, I haven't declared anything static and these are all, putatively, member functions. I tried it [on TakeAnAction and LookUp] when I got the error, but I got something like, 'Can't access MyPrivateMap from LookUp'. MyPrivateMap could be made public and I could refer to it directly, I guess, but my sensibility says that is not the right way to go about this [that means that namespace scoped helper functions are out, I think]. I also guess I could just inline the lookup and subsequent other stuff, but my line-o-meter goes on tilt. I'm trying desperately not to kludge it.

    Read the article

  • WCF Operation contract availability

    - by nettguy
    This question was asked at interview. Say I have a contract. [ServiceContract] public interface IMyService { [OperationContract] void methodForClientA(); [OperationContract] void AnothermethodForClientA(); [OperationContract] void methodForClientB(); [OperationContract] void AnothermethodForClientB(); } When a clientA access the contract it should only see the operation contracts void methodForClientA(),void AnothermethodForClientA(). Is it possible in WCF ?

    Read the article

  • Best Method For High Data Availability for SQL Server

    - by omatase
    I have a web service that runs 24/7. Periodically it needs to refresh its database with data from another web service. There is a lot of data. It's tens of thousands of rows. (no, I don't mean this is a lot of data for SQL Server, just trying to point out that I expect it to take some time to come down the pipe from the other web service) The data refresh can take between 5 and 10 minutes. The actual data update portion of that is between 1 and 2 minutes. This means the service would be down for all intents and purposes when consumers would be requesting this type of data. I would like to implement a system where data is always available. The only thing that comes to mind is some type of system where I maintain two separate databases. I populate the inactive one, swapping it to active before populating the other one. I'm not sure I know the best way to do this. My current ideas just revolve around two sets of the schema in a single database (using views to access the active set) or two databases each with the same schema. The application would rotate between the two databases. Any suggestions from someone who has done something like this before?

    Read the article

  • Windows Azure Worldwide availability

    - by Insomniac
    Hi, I've been reviewing Windows Azure platform for some time, and can't find answer to one very important question. If I deploy my application within a cloud, how it will be reached from different places worldwide? For example if I have a web application with a database and want it to be accessible to users in UK, US, China and etc. Can I be sure that any user in the world will get almost the same request processing time? I think of it this way. 1. User sends request (navigates in browser to my web site) 2. This request gets in a cloud in a nearest location (closest to user MS Data Center?) 3. It is processed by an instance of my web application (in nearest location, with request to my centralized DB which can be far away but SQL request goes via MS internal network, which I believe should be very fast). 4. Response sent to user. Please let me know if I'm wrong. Thanks.

    Read the article

  • Powershell - remote folder availability while counting files

    - by ziklop
    I´m trying to make a Powershell script that reports if there´s a file older than x minutes on remote folder. I make this: $strfolder = 'folder1 ..................' $pocet = (Get-ChildItem \\server1\edi1\folder1\*.* ) | where-object {($_.LastWriteTime -lt (Get-Date).AddDays(-0).AddHours(-0).AddMinutes(-20))} | Measure-Object if($pocet.count -eq 0){Write-Host $strfolder "OK" -foreground Green} else {Write-Host $strfolder "ERROR" -foreground Red} But there´s one huge problem. The folder is often unavailable for me bacause of the high load and I found out when there is no connection it doesn´t report an error but continues with zero in $pocet.count. It means it reports everything is ok when the folder is unavailable. I was thinking about using if(Test-Path..) but what about it became unavailable just after passing Test-Path? Does anyone has a solution please? Thank you in advance

    Read the article

  • PHP PDO Username Availability Checker

    - by John Bernal
    I'm building a registration page that uses JQuery's validator plugin to validate the form. For the username, i used the remote method. So here's my jquery+html code: fiddle And here's Available.php: <?php $usr = $_POST["username"]; $link = new PDO('mysql:***;dbname=***;charset=UTF-8','***','***'); $usr_check = $link->prepare("SELECT * FROM Conference WHERE Username = :usr"); $link->bindParam(':usr', $usr); $usr_check->execute(); if($usr_check->rowCount()>0) echo "false"; else echo "true"; ?> So I have a test account in my database with the username: user. When I tried to submit my form with the same username, it didn't display the error saying "username taken" which means the php isn't correct. Any ideas where I went wrong? Thanks

    Read the article

  • Feedback on availability with Google App Engine

    - by Ron
    We've had some good experiences building an app on Google App Engine, this first app's target audience are Google Apps users, so no issues there in terms of it being hosted on Google infrastructure. We like it so much that we would like to investigate using it for a another app, however this next project is for a client who is not really that interested in what technology it sits on, they just want it to work, and work all of the time. In this scenario, given that we have the technology applicability and capability side covered, are there any concerns that this stuff is still relatively new and that we may not be as much "in control" as if we had it done with traditional hosting?

    Read the article

  • Access to and availability of private member functions in C++

    - by David
    I am wandering the desert of my brain. I'm trying to write something like the following: class MyClass { // Peripherally Related Stuff public: void TakeAnAction(int oneThing, int anotherThing) { switch(oneThing){ case THING_A: TakeThisActionWith(anotherThing); break; //cases THINGS_NOT_A: }; }; private: void TakeThisActionWith(int thing) { string outcome = new string; outcome = LookUpOutcome(thing); // Do some stuff based on outcome return; } string LookUpOutcome(int key) { string oc = new string; oc = MyPrivateMap[key]; return oc; } map<int, string> MyPrivateMap; Then in the .cc file where I am actually using these things, while compiling the TakeAnAction section, it [CC, the solaris compiler] throws an an error: 'The function LookUpOutcome must have a prototype' and bombs out. In my header file, I have declared 'string LookUpOutcome(int key);' in the private section of the class. I have tried all sorts of variations. I tried to use 'this' for a little while, and it gave me 'Can only use this in non-static member function.' Sadly, I haven't declared anything static and these are all, putatively, member functions. I tried it [on TakeAnAction and LookUp] when I got the error, but I got something like, 'Can't access MyPrivateMap from LookUp'. MyPrivateMap could be made public and I could refer to it directly, I guess, but my sensibility says that is not the right way to go about this [that means that namespace scoped helper functions are out, I think]. I also guess I could just inline the lookup and subsequent other stuff, but my line-o-meter goes on tilt. I'm trying desperately not to kludge it.

    Read the article

  • Recaptcha - Availability in China

    - by wacdany
    We are developing a site that will require the usage of a captcha service. Has anyone successfully use Google Recaptcha (https://www.google.com/recaptcha/intro/index.html) for a website for users from Mainland China? Did you have major problems with load-time? Did you experience any reliability problems? Any problems with the great firewall of china? Any experience that you can share is appreciated.

    Read the article

  • 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.

    Read the article

  • Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

    - by vmiazzo
    Hi, Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not good for high availability. When 1 IP goes down clients will continue to use it for minutes. A load balancer is often suggested as a better choice. Both claims are not completely true: When the traffic is HTTP then, most of the HTML browsers are able to automatically try the next A record if the previous is down, without a new DNS look-up. Read here chapter 3.1 and here. When multiple data centers are involved then, DNS RR is the only option to distribute traffic across them. So, is it true that, with multiple data centers and HTTP traffic, the use of DNS RR is the ONLY way to assure instant fail-over when one data center goes down? Thanks, Valentino Edit: Off course each data center has a local Load Balancer with hot spare. It's OK to sacrifice session affinity for an instant fail-over. AFAIK the only way for a DNS to suggest a data center instead of another is to reply with just the IP (or IPs) associated to that data center. If the data center becomes unreachable then all those IP are also unreachables. This means that, even if smart HTML browsers are able to instantly try another A record , all the attempts will fail until the local cache entry expires and a new DNS lookup is done, fetching the new working IPs (I assume DNS automatically suggests to a new data center when one fail). So, "smart DNS" cannot assure instant fail-over. Conversely a DNS round-robin permits it. When one data center fail, the smart HTML browsers (most of them) instantly try the other cached A records jumping to another (working) data center. So, DNS round-robin doesn't assure session affinity or the lowest RTT but seems to be the only way to assure instant fail-over when the clients are "smart" HTML browsers. Edit 2: Some people suggest TCP Anycast as a definitive solution. In this paper (chapter 6) is explained that Anycast fail-over is related to BGP convergence. For this reason Anycast can employ from 15 minutes to 20 seconds to complete. 20 seconds are possible on networks where the topology was optimized for this. Probably just CDN operators can grant such fast fail-overs. Edit 3:* I did some DNS look-ups and traceroutes (maybe some expert can double check) and: The only CDN using TCP Anycast seems to be CacheFly, other operators like CDN networks and BitGravity use CacheFly. Seems that their edges cannot be used as reverse proxies. Therefore, they cannot be used to grant instant failover. Akamai and LimeLight seems to use geo-aware DNS. But! They return multiple A records. From traceroutes seems that the returned IPs are on the same data center. So, I'm puzzled on how they can offer a 100% SLA when one data center goes down.

    Read the article

  • Computer Networks UNISA - Chap 14 &ndash; Insuring Integrity &amp; Availability

    - by MarkPearl
    After reading this section you should be able to Identify the characteristics of a network that keep data safe from loss or damage Protect an enterprise-wide network from viruses Explain network and system level fault tolerance techniques Discuss issues related to network backup and recovery strategies Describe the components of a useful disaster recovery plan and the options for disaster contingencies What are integrity and availability? Integrity – the soundness of a networks programs, data, services, devices, and connections Availability – How consistently and reliably a file or system can be accessed by authorized personnel A number of phenomena can compromise both integrity and availability including… security breaches natural disasters malicious intruders power flaws human error users etc Although you cannot predict every type of vulnerability, you can take measures to guard against the most damaging events. The following are some guidelines… Allow only network administrators to create or modify NOS and application system users. Monitor the network for unauthorized access or changes Record authorized system changes in a change management system’ Install redundant components Perform regular health checks on the network Check system performance, error logs, and the system log book regularly Keep backups Implement and enforce security and disaster recovery policies These are just some of the basics… Malware Malware refers to any program or piece of code designed to intrude upon or harm a system or its resources. Types of Malware… Boot sector viruses Macro viruses File infector viruses Worms Trojan Horse Network Viruses Bots Malware characteristics Some common characteristics of Malware include… Encryption Stealth Polymorphism Time dependence Malware Protection There are various tools available to protect you from malware called anti-malware software. These monitor your system for indications that a program is performing potential malware operations. A number of techniques are used to detect malware including… Signature Scanning Integrity Checking Monitoring unexpected file changes or virus like behaviours It is important to decide where anti-malware tools will be installed and find a balance between performance and protection. There are several general purpose malware policies that can be implemented to protect your network including… Every compute in an organization should be equipped with malware detection and cleaning software that regularly runs Users should not be allowed to alter or disable the anti-malware software Users should know what to do in case the anti-malware program detects a malware virus Users should be prohibited from installing any unauthorized software on their systems System wide alerts should be issued to network users notifying them if a serious malware virus has been detected. Fault Tolerance Besides guarding against malware, another key factor in maintaining the availability and integrity of data is fault tolerance. Fault tolerance is the ability for a system to continue performing despite an unexpected hardware or software malfunction. Fault tolerance can be realized in varying degrees, the optimal level of fault tolerance for a system depends on how critical its services and files are to productivity. Generally the more fault tolerant the system, the more expensive it is. The following describe some of the areas that need to be considered for fault tolerance. Environment (Temperature and humidity) Power Topology and Connectivity Servers Storage Power Typical power flaws include Surges – a brief increase in voltage due to lightening strikes, solar flares or some idiot at City Power Noise – Fluctuation in voltage levels caused by other devices on the network or electromagnetic interference Brownout – A sag in voltage for just a moment Blackout – A complete power loss The are various alternate power sources to consider including UPS’s and Generators. UPS’s are found in two categories… Standby UPS – provides continuous power when mains goes down (brief period of switching over) Online UPS – is online all the time and the device receives power from the UPS all the time (the UPS is charged continuously) Servers There are various techniques for fault tolerance with servers. Server mirroring is an option where one device or component duplicates the activities of another. It is generally an expensive process. Clustering is a fault tolerance technique that links multiple servers together to appear as a single server. They share processing and storage responsibilities and if one unit in the cluster goes down, another unit can be brought in to replace it. Storage There are various techniques available including the following… RAID Arrays NAS (Storage (Network Attached Storage) SANs (Storage Area Networks) Data Backup A backup is a copy of data or program files created for archiving or safekeeping. Many different options for backups exist with various media including… These vary in cost and speed. Optical Media Tape Backup External Disk Drives Network Backups Backup Strategy After selecting the appropriate tool for performing your servers backup, devise a backup strategy to guide you through performing reliable backups that provide maximum data protection. Questions that should be answered include… What data must be backed up At what time of day or night will the backups occur How will you verify the accuracy of the backups Where and for how long will backup media be stored Who will take responsibility for ensuring that backups occurred How long will you save backups Where will backup and recovery documentation be stored Different backup methods provide varying levels of certainty and corresponding labour cost. There are also different ways to determine which files should be backed up including… Full backup – all data on all servers is copied to storage media Incremental backup – Only data that has changed since the last full or incremental backup is copied to a storage medium Differential backup – Only data that has changed since the last backup is coped to a storage medium Disaster Recovery Disaster recovery is the process of restoring your critical functionality and data after an enterprise wide outage has occurred. A disaster recovery plan is for extreme scenarios (i.e. fire, line fault, etc). A cold site is a place were the computers, devices, and connectivity necessary to rebuild a network exist but they are not appropriately configured. A warm site is a place where the computers, devices, and connectivity necessary to rebuild a network exists with some appropriately configured devices. A hot site is a place where the computers, devices, and connectivity necessary to rebuild a network exists and all are appropriately configured.

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 3 4 5 6 7 8 9 10 11 12 13 14  | Next Page >