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• Load-balancer options

  - by toolkit

  I am looking at a number of possible options for load-balancing. So far, I am constrained to the following options: DNS server load-balancer, balancing to a cluster of tomcat servers, with terracotta for session replication. Pros - don't have to buy new kit. Cons - DNS lb can keep directing to a broken server. Hardware load-balancer, direct to cluster of tomcat servers. Pros - could have second box for failover lb. Cons - expense. Apache server load-balancer. Pros - apache's lb polls for broken servers. Cons - apache server is single point of failure, plus need to buy another server. Are there any other options I should consider? Thanks. Update: Thanks for all the answers so far +1's all round. Not accepting an answer yet, to keep more ideas coming.

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• Is it possible to a VM inside a VM (e.g., KVM on Vmware)?

  - by lorin

  I'd like to do some development on Eucalyptus, an open source project which provides an Amazon EC2 interface for launching virtual machine instances on a collection of privately managed nodes. I'd really like to be able to do some of the development on my desktop, rather than having to deploy Eucalyptus on our shared local cluster each time I make a change to the source code. (Especially since there are a group of us sharing that test cluster). Unfortunately, my desktop machine is a Mac, which won't run Eucalyptus natively. I do have VMWare Fusion, and it would be really nice if I could do my Eucalyptus testing inside a VMWare instance. The problem is, to test out Eucalyptus, it will have to launch (KVM or Xen) VM instances. I've got no idea if it's possible to actually launch a KVM or Xen instance inside a VMWare instance.

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• BackupExec 12 to Bacula questions

  - by LVDave

  We have a 128 node compute cluster for environmental modeling, with a master/head node which we currently backup with a Windows2003 system running BackupExec 12 and a single HP LTO3 tape drive. We have recently ordered an Overland NEO200s 12 slot library, and are considering migrating off Windows to CentOS 5 for the backup server. The master/head node is RHEL5, with the compute nodes currently being migrated from a mix of RHEL3/4/5 to CentOS5. I'm fairly familiar with RH/Centos, but have no experience with Bacula. We've tentatively settled on Bacula as our cluster vendor recommended it. My questions are: 1) Does Bacula support an Overland NEO200s/LTO3 library? 2) Can Bacula catalog/restore tapes written by BE? and 3) I've head of Amanda, but am even more unfamiliar with it than Bacula. Any assistance would be appreciated Dave Frandin

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• Could we build a mega-processor out of superconductors?

  - by Carson Myers

  A superconductor, once cooled below a critical temperature, loses all of its electrical resistance and therefore becomes 100% efficient. This means that when a current flows through a superconductor, none of the energy is lost to heat or light. Theoretically, could we build a processor out of superconductive materials, that could effectively run at, oh I don't know, say, 300ghz? or 5,000ghz? Since a superconductive circuit is 100% efficient, this means that once supplied with electricity, the source of power could be completely removed from the circuit and the current would continue to flow forever. So if we made all the components inside a computer out of superconductive materials, could we get away with only supplying power to the peripherals and save a-whole-lot on energy, while dramatically increasing computing speed? Might this be one of the next big breakthroughs in computing? What do you think?

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• How do I debug this FS error on a flash device?

  - by abc

  I have console access to an embedded linux device. This device has flash memory part of which is partitioned as a FAT filesystem. Its running linux-2.6.31. However I am seeing these errors on the console these days and the FAT file system becomes read only. 111109:154925 FAT: Filesystem error (dev loop0) 111109:154925 fat_get_cluster: invalid cluster chain (i_pos 0) 111109:154925 FAT: Filesystem error (dev loop0) 111109:154925 fat_get_cluster: invalid cluster chain (i_pos 0) I cannot understand why this happened? What is the root cause? And what is the fix? I would appreciate answers that can point me how to investigate the possible root cause of this issue on the device.

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• OSX: Selecting default application for all unknown and different file types (extensions)

  - by Leo

  I work in cluster computing and am using Mac OS X 10.6. I send off hundreds of computing jobs a day, and each one comes back with with a different extension. For example, svmGeneSelect.o12345 which is the std output of my svmGeneSelect job which is job number 12345. I don't control the extensions. All files are plain text. I want OSX to open any file extension that it hasn't seen before with my favorite text editor when I click on it. Or even better set up file association defaults for extension patterns ie textEdit for extensions matching *.o*. I do NOT want to create file associations for individual files since this extension will only ever exist once, and I do not want to go through the process of selecting the application to use for each file. Thanks for any help you can offer.

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• How do you handle reboots?

  - by Mart

  We have one VPS (Windows 2008 R2+IIS7.5), with an asp.net mvc 3 application. The main question is: how to handle issues when Windows needs to reboot? (after installing Windows Updates or anything else). The goal is to make the website 24/7, but first it's ok to show a message to the users. (we'll be back soon, something like app_offline.htm) Our application uses SQL and also writes/reads some files (uploaded photos, documents) which are not stored in SQL. What do you recommend? Load balancing with ARR? (with 1+2 servers, but what if the front-end server needs reboot?) Windows failover cluster? SQL failover cluster? What to do with uploaded files? I really don't know what would be the best (and simplest) solution.

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• BixData or Zabbix?

  - by Arafat

  Hi all, I've been using Ganglia to monitor my single Mac OSX server which runs Apache and MySQL. I'm ok with it. Now we are upgrading our servers, 6 IBM X3650 M3 and 2 Fujitsu servers. 2 IBM for Apache cluster and 4 IBM for MySQL NDB Cluster. The other two servers are for Load balancers. All servers are going to run Debian Lenny 5 on it. Now I need to decide on which monitoring tool I should go for. I found that BixData and Zabbix does an excellent job than Ganglia, in terms of sensors and reporting. Have anyone tried the above two tools? And which tool would you suggest me? For Debian. As I'm writing this, I'm installing BixData to try.... Thanks in advance.

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• can't connect to Sql Sever Management Express 2012

  - by Rare-Man

  i installed Sql Sever Management Express 2012 , but when i try to connect in Sql management studio enviroment , i have this error . TITLE: Connect to Server Cannot connect to .. ADDITIONAL INFORMATION: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 2) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&EvtSrc=MSSQLServer&EvtID=2&LinkId=20476 The system cannot find the file specified BUTTONS: OK ................................................................................... and in during installion i dont have option for select cluster !! this is my SQL Server Configuration Manager , my sql server service is empty ... And when get Remove a Failover Cluster Node , this error happened . http://oi57.tinypic.com/2lrvat.jpg

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• (simple) linux HA with vmware vsphere?

  - by derhelge

  I hope my upcoming question is specific enough, and you are able and willing to support :-) We have several openSUSE VMs in an ESX-Cluster (three ESX-Servers) with an attached iSCSI-SAN. All of those Linux VMs are "single point of failure"-configured, which means in the case of a Web-Server: LAMP, storage, etc. everything on this machine. This was very simple and in case of a failure (in the last years: kernel panics or apache crashes) a simple reboot triggered by a script did it. But the problem is: How to upgrade/maintain the w(eb-)application or the underlying OS without downtime? This wasn't really managable and i did this in the early morning ;) How can i achieve a "simple" High-Availability Cluster now? I thought of: DRBD with heartbeat with 2 VMs. And for the storage a RDM (raw device mapped) LUN and change the read-write-permissions for both VMs. Is this a good idea? Anyone has a better solution?

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• configure cisco catalyst 3560g with an egress uplink

  - by imaginative

  Currently my setup has our egress uplink connected directly to an external interface on a linux router/firewall/nat gateway. Since the linux box is a single point of failure, I've since setup two openbsd boxes using carp+pf+pfsync in order to gain some additional redundancy. the problem is, I only have one egress uplink (it's still a single point of failure) but need to get it to speak to the active carp node in my openbsd cluster which will server as my new router/firewall/nat cluster. Is there anything specific I need to do on a 3560G in order for me to be able to: 1) Drop the egress uplink into a port 2) Drop one link from the switch to a firewall 2) Drop a second link from a switch to the firewall This is so if one box dies, the other still has the egress link to the switch. Is putting them into one VLAN enough? Anything else that needs to go into the configuration for this setup to work?

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• libvirt + ESX (HTTP response code 400 for call to 'Login')

  - by Coops

  I'm trying to connect to a vSphere cluster using the information from the libvirt documentation. $ virsh -c "vpx://[email protected]/dc1/dc1-cluster-e01/dc1-vsphere-e04/?no_verify=1" Enter root's password for 10.51.4.11: error: internal error HTTP response code 400 for call to 'Login' error: failed to connect to the hypervisor I seem to be able to establish a connection, but it fails with a "HTTP code 400". If I provide the incorrect password it fails with a 'login credentials' error, so it looks like I am getting a connection, but it's failing for another reason. Wireshark is no help as it's all done over SSL/TLS. Any thoughts folks? UPDATE: 15:21 28/02/11 FYI - I'm running libvirt-0.8.3 (the Ubuntu package recompiled with the ESX flag enabled). When I put virsh into debug mode it returns this: [snip] Enter root's password for 10.51.4.11: 15:19:09.011: debug : do_open:1249 : driver 3 ESX returned ERROR 15:19:09.011: debug : virUnrefConnect:294 : unref connection 0x98aa8f8 1 15:19:09.011: debug : virReleaseConnect:249 : release connection 0x98aa8f8 error: internal error HTTP response code 400 for call to 'Login' error: failed to connect to the hypervisor

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• DPM Coordinator Service is not responding

  - by Anatoly Vilchinsky

  Hi dear Gurus! I'm in stuck point now, so please at least try to help me. I've installed DPM 2010 on cluster server (w2k8 r2), everything was fine. Than I've tried tot install Protection Agent on both server of my cluster, but I'm getting error Error 312: The agent operation failed because the DPM Agent Coordinator service is not responding. Error details: The service cannot be started, either because it is disabled or because it has no enabled devices associated with it (0x80070422) Recommended action: Restart the DPM Agent Coordinator service on . And the thing is that I'm totally can't see DPM Agent Coordinator service not on the localhost, nor on the second server. All the suggestion, that I've found in the internet are suggesting to restart this service, but how can I perform this if the one is absent? I'll be glad for any help

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• Horrible performing RAID

  - by Philip

  I have a small GlusterFS Cluster with two storage servers providing a replicated volume. Each server has 2 SAS disks for the OS and logs and 22 SATA disks for the actual data striped together as a RAID10 using MegaRAID SAS 9280-4i4e with this configuration: http://pastebin.com/2xj4401J Connected to this cluster are a few other servers with the native client running nginx to serve files stored on it in the order of 3-10MB. Right now a storage server has a outgoing bandwith of 300Mbit/s and the busy rate of the raid array is at 30-40%. There are also strange side-effects: Sometimes the io-latency skyrockets and there is no access possible on the raid for 10 seconds. The file system used is xfs and it has been tuned to match the raid stripe size. Does anyone have an idea what could be the reason for such a bad performing array? 22 Disks in a RAID10 should deliver way more throughput.

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• Cannot WMI Query root\MSCluster namespace as Local Admin

  - by Matt Zuberko

  I'm trying to use WMI Explorer to query the root\MSCluster namespace on various hosts to obtain cluster resource group and resource object data. I can access the namespace with no issue on Win2K3 cluster nodes but am getting an access denied error attempting to connect to Win2K8 and Win2K8R2 nodes. I can access the root\cimv2 namespace with no issue, just the MSCluster namespace even though I am a local Admin. Is there a feature setting, local security policy or server role I have to be a member of to access the namespace? Thank you!

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• apache tomcat loadbalancing clustering on ubuntu

  - by user740010

  i am facing a problem in clustering the tomcat with apache as a loadbalancer using mod_jk on ubuntu. i have install apache2 on my ubuntu 11.04 and i have downloaded tomcat7 created two copies and kept them at two different location. 1st one is at /home/net4u/vishal/test/tomcatA 2nd one is at /home/net4u/vishal/test1/tomcatB i have made following changes to server.xml file in /conf folder 1. <Server port="8205" shutdown="SHUTDOWN"> 2. <Connector port="8280" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> 3.<Connector port="8209" protocol="AJP/1.3" redirectPort="8443" /> <Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcatB"> 4. <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> similarly i have modified other tomcat i.e tomcatA server.xml content of the server.xml is as follow: -- <!--The connectors can use a shared executor, you can define one or more named thread pools--> <!-- <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/> --> <!-- A "Connector" represents an endpoint by which requests are received and responses are returned. Documentation at : Java HTTP Connector: /docs/config/http.html (blocking & non-blocking) Java AJP Connector: /docs/config/ajp.html APR (HTTP/AJP) Connector: /docs/apr.html Define a non-SSL HTTP/1.1 Connector on port 8080 --> <Connector port="8280" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <!-- A "Connector" using the shared thread pool--> <!-- <Connector executor="tomcatThreadPool" port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> --> <!-- Define a SSL HTTP/1.1 Connector on port 8443 This connector uses the JSSE configuration, when using APR, the connector should be using the OpenSSL style configuration described in the APR documentation --> <!-- <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true" maxThreads="150" scheme="https" secure="true" clientAuth="false" sslProtocol="TLS" /> --> <!-- Define an AJP 1.3 Connector on port 8009 --> <Connector port="8109" protocol="AJP/1.3" redirectPort="8443" /> <!-- An Engine represents the entry point (within Catalina) that processes every request. The Engine implementation for Tomcat stand alone analyzes the HTTP headers included with the request, and passes them on to the appropriate Host (virtual host). Documentation at /docs/config/engine.html --> <!-- You should set jvmRoute to support load-balancing via AJP ie : <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1"> --> <Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcatB"> <!--For clustering, please take a look at documentation at: /docs/cluster-howto.html (simple how to) /docs/config/cluster.html (reference documentation) --> <!-- uncomment for clustering--> <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> <!-- Use the LockOutRealm to prevent attempts to guess user passwords via a brute-force attack --> <Realm className="org.apache.catalina.realm.LockOutRealm"> <!-- This Realm uses the UserDatabase configured in the global JNDI resources under the key "UserDatabase". Any edits that are performed against this UserDatabase are immediately available for use by the Realm. --> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true"> <!-- SingleSignOn valve, share authentication between web applications Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.authenticator.SingleSignOn" /> --> <!-- Access log processes all example. Documentation at: /docs/config/valve.html Note: The pattern used is equivalent to using pattern="common" --> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log." suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" resolveHosts="false"/> </Host> </Engine> i have install libapache2-mod-jk step 1. i have Created jk.load file in /etc/apache2/mods-enabled/jk.load content is as follows: LoadModule jk_module /usr/lib/apache2/modules/mod_jk.so Create /etc/apache2/mods-enabled/jk.conf: JkWorkersFile /etc/apache2/workers.properties JkLogFile /var/log/apache2/jk.log JkMount /ecommerce/* worker1 JkMount /images/* worker1 JkMount /content/* worker1 step 2. Created workers.properties file in /etc/apache2/workers.properties content is as follows: workers.tomcat_home=/home/vishal/Desktop/test/tomcatA workers.java_home=/usr/lib/jvm/default-java ps=/ worker.list=tomcatA,tomcatB,loadbalancer   worker.tomcatA.port=8109 worker.tomcatA.host=localhost worker.tomcatA.type=ajp13 worker.tomcatA.lbfactor=1   worker.tomcatB.port=8209 worker.tomcatB.host=localhost worker.tomcatB.type=ajp13 worker.tomcatB.lbfactor=1 worker.loadbalancer.type=lb worker.loadbalancer.balanced_workers=tomcatA,tomcatB worker.loadbalancer.sticky_session=1 i tried the same thing on the windows machine it is working.

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• How do I remove Slony from a restored PostgreSQL database?

  - by Scott Herbert

  I've restored a database which came from a server on which Slony was running. The server on which the database has been restored does not have Slony installed. When the database restored, there were a lot of errors reported, with Slony related objects not getting created due to Slony related logins being missing. This I thought was not a problem, as losing the Slony objects didn't seem to matter, and infact seemed desirable. However, now I've got an anoying, if not critical problem. Whenever one clicks on a table in the newly restored DB in PGAdmin, a Slony related error popup ... pops up. The first one reads: "An error has occured: ERROR: function _rmscl.getlocalnodeid(unknown) does not exist" I notice that under the Replication node in PGAdmin, that there is a Slony replication cluster. Trying to drop this cluster results in more object missing type errors. Does anyone have any ideas how we can remove the last vestiges of Slony from this database?

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• VMware Virtual vCenter and High Availability

  - by rufo

  To continue with this question: Should be Vmware vCenter server high available? According to the response there even if vCenter is down HA will continue to work. So, if my vCenter is a VM, using the express sql edition in the same VM, and that VM is hosted in the same cluster it manages (and the cluster is setup for HA): Am I correct to assume that if the host that hosts the vCenter goes down HA will vmotion the vCenter VM to another host and it will continue to function? BTW: my environment is small, two ESXi 5.0 hosts, with about 50 VMs, using iSCSI shared storaged for everything.

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• NLB RPC server is unavailable on the specified computer

  - by Robin Weston

  Hi guys, Firstly, I'll admit that my networking knowledge is limited so as people request more information I'll update this question accordingly. I am trying to create a NLB Cluster across 2 Windows Server 2008 Web Servers. Neither of the machines are members of a domain, and both have 2 NICs (one for processing external web traffic, and one for communicating internally). I have installed NLB on both machines, and have created a cluster on Host A and added itself to it. However, when I try and add Host B (using the address from the external NIC) I get the following error : "The RPC server is unavailable on the specified computer". On Host B I can see that the RPC service is running fine. I can also ping and RDP from Host A to Host B with no problems either. I have disabled the windows firewall on both machines but that had no effect

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• How to find date/time used by Cassandra

  - by JDI Lloyd

  Earlier this morning I noticed that one of the nodes in our Cassandra cluster is writing logs an hour in the future, despite the date/time being correct on the OS. A couple of other nodes I checked via logs appear to be writing logs at the correct time. I now need to go through and check each node in our 80 node cluster and ensure cassandra is running on the correct time, problem being is some of the nodes don't write to the logs very often as they aren't doing much... the question is, is there some form of tool/utility (ie nodetool) that can tell me the time that cassandra is running on? All the systems date/times are correct, ntpdate cron in place has been for a while. Servers are set to Belize timezone to avoid DST changes so its nothing to do with that.

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• sectors and clusters

  - by Phenom

  Are the sectors in a cluster all next to each other?

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• Normalize Accept-Encoding via HAProxy for optimized Squid hit rate

  - by Matt Beckman

  Our website infrastructure uses HAProxy for load balancing, a Squid cluster for caching, and application data is on an IIS cluster. We load balance HAProxy by URI to optimize the Squid hit-rate, but we know that Squid is holding different copies of each page based on the Accept-Encoding header passed to it by the browser, and so IE (gzip, deflate) will have a different copy of a cached page than Firefox (gzip,deflate) or Chrome (gzip,deflate,sdch). We want to normalize the Accept-Encoding headers and I think the best place to do so would be in HAProxy. I'd appreciate it if someone could offer some ideas on how to accomplish this without breaking support for clients without gzip or deflate support.

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• redundant/multi-site terminal server

  - by Adam

  Hi We have a Hyper-V cluster running 5 virtual terminal servers using HA. We need to be able make this system redundant and so if this site was to fail our users could log into the backup system at another location and access their data via the terminal servers. Any ideas? We were thinking of maybe using a NAS which replicated the data to the other location in real-time(pass-through disks)? and having a similar Hyper-V cluster setup in the backup location. However we would need to create the users in both location and create a virtual mirror without the data ie applications, directories, settings etc. Is this the best way to achieve this? We have read that using Hyper-v pass through disks is a big performance de-grade.

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• Linux Security/Sysadmin Courses in London?

  - by mister k

  Hi, My employer has offered to send me on a couple of training courses and I'm just looking for some recommendations. I'm mainly looking to improve my security and general sysadmin skills. I would like to do something focused on UNIX as I mainly work with Linux boxes (but also a couple of FreeBSD boxes). I don't want to do a study-from-home course, so I would need to find somewhere based in London. It would be great to hear from anyone who has some experience with this kind of course. The courses I've found so far are: www.learningtree.co.uk/courses/uk433.htm www.city.ac.uk/cae/cfa/computing/systems_it/linux.html www.city.ac.uk/cae/cfa/computing/systems_it/unix_tools_ss.html I'm not sure the City University courses are advanced enough as I already have experience... Thanks!

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• Windows 7 PC refuses to join domain

  - by Alex

  So, we're wiping clean all PCs at our office and migrating them to a new server cluster and a new domain. Last night I tested on PC and it mostly worked except it refuses to join to the domain. Now, our domain is named like EXAMPLE.COM. When I just type EXAMPLE the PC can't find the domain controller, even though I can ping it find. If I type EXAMPLE.COM it seems to work. How can I get it to work with just EXAMPLE? That's how I got all the new servers int he cluster to work (about 20 of them) and I haven't had any issues... The only difference between the Windows 7 PC(s) and the servers is that the clients will be on a 10.0.3.X network where as the servers are on a 10.0.1.X network. Oh, the domain controller and all the other servers are Windows Server 2008 R2. Suggestions will be highly appreciated!

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