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• Delayed internet access

  - by Joel Coel

  When I (and presumably my users) first start up or log in to my computer I can't get internet access until several minutes after logging in. Internet pages like serverfault.com will time out. During this time I can access internal web servers. Sometimes pinging the gateway seems to fix the problem. I'm using Windows 7 on this machine with wifi, and the problem seems limited to the wifi network, which is on a separate vlan. The wired network does not share the problem, but I know it's not the wifi connection itself because the internal sites work. The wifi access point is attached to a 3Com 4200 switch, with the port set for vlan 2 untagged, vlan 1 tagged. The 4200 has a fiber connection to a 3Com 4900SX fiber switch that acts almost as a router here. The fiber connection is vlan 1 untagged vlan 2 tagged at both ends. The gateway is then attached to a different 4200 (vlan 1 untagged, vlan 2 tagged) that has a similar fiber connection to the 4900SX. vlan 2 has 192.168.8.0/22 IPs, vlan 1 has 10.1.0.0/16 IPs. The 4900SX has an interface for both vlans (10.1.1.1/192.168.8.1), as does the gateway (10.1.1.5/192.168.8.5). There is one dchp server for both vlans on the same switch as the gateway. It chooses a dhcp scope based on the interface used by the 4900sx to forward the dhcp request. There is also a network access list on the 4900sx set to deny all vlan2 traffic to any 10.1.x.x host, with exceptions made for a few servers, including dhcp, 4900sx, and the gateway. I think that about covers it. Any ideas on why internet access would be delayed like this?

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• Different subnets routing with just one layer 3 switch

  - by GustavoFSx

  Our current network looks like this: Location 1: 2 Layer 2 switches | subnet 192.168.1.0/24 | Firewall for our VPN Location 2: 1 Layer 2 switch | subnet 192.168.3.0/24 | Firewall for our VPN Location 3: 1 Layer 2 switch | subnet 192.168.5.0/24 | Firewall for our VPN We just got a direct fiber connection between location 1 and 2, we also got a new HP V1910 24G layer 3 switch. I tried to follow the instructions on this site, but I can't get it to work. I think our network should look like this: Location 1: HP Switch FIBER to L2 | subnet 192.168.1.0/24 | Firewall for our VPN Location 2: 1 Layer 2 switch | subnet 192.168.3.0/24 | FIBER to L1 Location 3: 1 Layer 2 switch | subnet 192.168.5.0/24 | Firewall for our VPN So, how can I get routing working on our location 2? It's old gateway was a firewall device on ip 192.168.3.1. I'm thinking on creating a VLAN Interface on 192.168.3.1 on the switch for the Location 2. But how will I handle that on the HP switch that has a direct fiber connection with that switch? Please help, I'm not very good with networking.

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• Wheaties Fuel = Wheaties FAIL

  - by Steve Bargelt

  Are you kidding me? What a load of nutritional CRAP. Don’t buy this product. Just don’t do it. They are just like Wheaties with more sugar and fat. Awesome just what we need more sugar!! Okay now I’m not against carbs… I’m really not. Being a cyclist I realize the importance of carbohydrates in the diet… but let’s be realistic here. Even though the commercials for Wheaties Fuel say they are for athletes you know that what General Mills is really hoping for is that kids will see Payton Manning, Albert Pujols and KG and buy this cereal and eat a ton of it for breakfast. Sad, really. I’ve watched all the videos and read all the propaganda on the Wheaties Fuel web site and no where do they talk about why they added sugar and fat the original Wheaties. There is a lot of double-speak by Dr. Ivy about “understanding the needs of athletes.” I had to laugh – in one of the videos Dr. Ivy even says that he thinks the "new Wheaties will have even more fiber! Wrong! My bad... there is 5g of fiber not 3g per serving. Just  Way more sugar. A serving of FROSTED FLAKES has less sugar per serving!!!   Wheaties Fuel Wheaties Frosted Flakes Honey Nut Cheerios Quaker Oatmeal Serving Size 3/4 cup 3/4 cup 3/4 cup 3/4 cup 3/4 cup Calories 210 100 110 110 225 Fat 3g .5g 0g 1.5g 4.5g Protein 3g 3g 1g 2g 7.5g Carbohydrates 46g 22g 27g 22g 40.5g Sugars 14g 4g 11g 9g 1.5g Fiber 5g 3g 1g 2g 6g   In reality it might not be a bad pre-workout meal but for a normal day-in-day-out breakfast is just seems to have too much sugar - especially when you bump the serving size up to 1 to 1.5 cups and add milk! I’ll stick with Oatmeal, thank you very much.

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• Is minimum latency fixed by the speed of light?

  - by JavaRocky

  Suppose i had a fiber optic link from one side of the planet to the other side of the planet. Is it safe to say, that with current technology, the latency of communication can never be reduced? Understand that a fiber optic cable is not a perfect medium thus data only travels close to the speed of light. Also lets consider that i will not be drilling a hole thru the center of the earth and it is just running along the ocean.

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• Redundant Connection Issue

  - by Adam

  I'm trying to set up a redundant connection for our web hosting servers. I have a BGP-capable router connecting two lines from two separate ISP's, one fiber (primary), one DSL (failover). I've already confirmed that I can push routes into the DSL ISP's system, so long as they aren't malicious. My question is, what do I need to do on the fiber side to make those IP's routable through the DSL? Is there something I'm missing?

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• Improving Performance of RDP Over LAN

  - by Jared Brown

  Architecture: A deployment of 6 new HP thin clients (Windows XP Embedded) with TCP/IP access to several new HP servers (Windows 2003 Server). Each thin client is connected over fiber optic to a Gigabit Cisco switch, which the servers are connected to. There are 10/100 Ethernet to fiber converter boxes on each end of the fiber cables. Problem: Noticeable lag over RDP while using the Unigraphics CAD package. 3D models take .5 to 1 second to respond to mouse actions. Other Details: Network throughput on each thin client's RDP session is 7288 kbps. RDP connection settings - color setting: 15k, all themes, etc. turned off. Local and remote system performance stats are well within norms (CPU, Memory, and Network). Question: Are there newer versions of terminal services or RDP I can use on my existing OSes? Are there compression algorithms, etc. that are well suited for a high-bandwidth LAN? Are there valid alternatives that will yield higher performance (i.e. UltraVNC with drivers installed)? Are there TCP/IP tuning options I can exploit?

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• Bandwidth Suggestion

  - by Campo

  I have been asked to analyze the bandwidth usage of a company and make a recommendation for upgrading their Internet connection(s). Here is the layout 3 DLS lines so it is 3x(6 Down, 1 Up Each) into a load balancer out to the office's network. 30 VOIP phones run on a T1 (1.5 Down, 1.5 Up) The users at the company are heavily uploading. It is my suspicion that the issue in slowdown is being cause by multiple people uploading and others not being able to get requests out for even simple http requests. My initial idea is to get them a fiber line with a 10 down and 10 up. What do others think on this plan? Will that be enough to host their network traffic? What do I do about the VOIP line afterward? The fiber is expensive and I know the T1 does a great job for their VOIP so I do not want to suggest a DSL line because I know it may not be sufficient. I would also like to save them some money if I can. Maybe even get a faster fiber line and forgo the T1. Though I know their load balance/switch can only handle 20MB/S throughput. Looking for some confirmation/suggestions on my plan. I am planning on going in to get some real diagnostic numbers. Any suggestions on software to use for that? Preferably Windows software.

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• Why are ISP's installing routers on my site when the feed is a form of ethernet already?

  - by Cosmin Prund

  I'm connected to 3 ISP's right now. Two of them already have routers at my site, the third one announced me "they need to install some equipment" when I requested BGP session. I can only assume they need to install a Router, since that connection is now working fine, using the usual /30 net block for the connection, and the "last-mile" solution is not going to change since they only installed it last week and the BGP was in the contract from the beginning. I simply don't understand this: the "feed" is already a form of ethernet. Even those they're using different technologies for the last mile, they're all entering the ISP router using an RJ45 WAN port. I assume the ISP router does something really important that can't be done by the Big Router on the other end of the connection. It must also be something that can hurt them if miss-configured, since they don't trust us (the client) to do the stuff on our router. And I'm not talking cheap throw-away routers here: One of the routers is Cisco 2800. Edit to add network details: I'm connected to 3 ISP's, two over Radio links, one over Fiber Optic. One of the radio links is going to get dropped and the other radio link will be turned into fiber sometime next year. The fiber is 20 Mbit, radio 1 is 40 Mbit and radio 2 is 2 Mbit. I've got a /24 of provider independent address space. I'm not doing out-of-the ordinary stuff with my network, I'm overly connected because my network needs to be "up" all the time.

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• Hyper-V Live Migration across Sites!

  - by Ryan Roussel

  One of the great sessions I sat in on at Tech Ed this week was stretching a Windows 2008 R2 Hyper-V  Failover Cluster across sites.  With this ability, you could actually implement a Hyper-V cluster where you could migrate or even Live Migrate VMs across sites.   With this area’s propensity for Hurricanes, this will be a very popular topic for me over the next few months. While this technology is possible today, it’s also very complicated and can be very expensive to implement.    First your WAN connection has to support the ability to trunk your VLAN across both sites in order to Live Migrate.  This means you can’t use a Layer 3 routed connection like MPLS.  It has to be a Metro Ethernet connection or "Dark Fiber”.  Dark Fiber is unused Fiber already in the ground that can be leased from  various providers. Both of these connections would allow you to trunk layer 2 across your WAN.  Cisco does have the ability to trunk layer 2 across a routed connection by muxing the traffic but this is only available in their Nexus product line which has a very steep price tag.   If you are stuck with MPLS or the like and Nexus switching is not a realistic possibility, you will have to implement a multi-subnet cluster in which case Live Migration won’t be possible.  However you can still failover VMs to the remote site with some planning and manual intervention.  The consideration here is that the VMs will be on a different subnet once migrated, so you will have to change the IP addressing of your VMs.  This also has ramifications with DNS and Name resolution to control your down time.  DHCP with Reservations for your VMs is the preferred method to achieve the IP changes as this will automate that part of the process.   Secondly, you will have to have  a mechanism to replicate your storage across both sites.  Many SAN vendors natively support hardware based synchronous and asynchronous replication.  Some even support cluster shared volumes which were introduced in 2008 R2.   If your SANs do not support this natively, there are alternative file based replication products either software based like Double Take or hardware appliance like EMC.  Be sure to check with your vendor on the support of Disk majority if you’re replicating your quorum disk between SANs.   The last consideration is the ability to maintain quorum for your cluster.  If your replication provider does not support Disk Majority through replication, you will have to explore Node Majority with File Share Witness.  This will affect your design as a 3 node cluster with 1 node at the remote site and FSW at the production site would not have the ability to maintain quorum if the production site was lost. MS best practice for this would be to implement an even node cluster with 2 nodes at  each site and the FSW at a third site.   And there you have it.  While some considerations and research goes into implementing this solution, even a multi-subnet solution would be invaluable to organizations in the implementations of “warm” DR sites.

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• Flex - Increase timeout on a PHP service function call

  - by Travesty3

  I'm using Flash Builder 4 Beta 2. I have it connecting to a PHP service. The way I set this up was using the wizard, so I didn't actually write the code to connect to it. The service looks like this: package services.flash { import mx.rpc.AsyncToken; import com.adobe.fiber.core.model_internal; import mx.rpc.AbstractOperation; import valueObjects.CustomDatatype8; import valueObjects.NewUsageData; import mx.collections.ItemResponder; import mx.rpc.remoting.RemoteObject; import mx.rpc.remoting.Operation; import com.adobe.fiber.services.wrapper.RemoteObjectServiceWrapper; import com.adobe.fiber.valueobjects.AvailablePropertyIterator; import com.adobe.serializers.utility.TypeUtility; [ExcludeClass] internal class _Super_FLASH extends RemoteObjectServiceWrapper { // Constructor public function _Super_FLASH() { // initialize service control _serviceControl = new RemoteObject(); var operations:Object = new Object(); var operation:Operation; operation = new Operation(null, "sendCommand"); operation.resultType = Object; operations["sendCommand"] = operation; ... } } One of the functions that I'm calling fetches users from a MySQL database. There are about 30,000 users right now. The service seems to timeout when fetching more than around 22,000 rows, I get the "Channel Disconnected before an acknowledgement was received" error. If I call the PHP script from a browser, it fetches them all with no problems at all, however. I have tried increasing the timeout in the PHP script (which didn't work), but obviously this isn't the problem since the browser is able to pull them up with no problems. Is there a way to increase the timeout of the PHP service in Flash Builder? I'm a bit of a noob when it comes to Flash, so please be descriptive. Thanks in advance!

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• What kind of storage do people actually use for VMware ESX servers?

  - by Dirk Paessler

  VMware and many network evangelists try to tell you that sophisticated (=expensive) fiber SANs are the "only" storage option for VMware ESX and ESXi servers. Well, yes, of course. Using a SAN is fast, reliable and makes vMotion possible. Great. But: Can all ESX/ESXi users really afford SANs? My theory is that less than 20% of all VMware ESX installations on this planet actually use fiber or iSCS SANs. Most of these installation will be in larger companies who can afford this. I would predict that most VMware installations use "attached storage" (vmdks are stored on disks inside the server). Most of them run in SMEs and there are so many of them! We run two ESX 3.5 servers with attached storage and two ESX 4 servers with an iSCS san. And the "real live difference" between both is barely notable :-) Do you know of any official statistics for this question? What do you use as your storage medium?

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• kSOAP2 and SOAPAction on Android

  - by Matze

  Hi everyone, I am trying to access a Webservice with kSOAP2 on an Android Phone. I think the connection is being established, but the server won't answer my request since I'm not providing a SOAP Action Header which seems to be required in SOAP Version 1.1(please correct me if I'm wrong here) which I have to use since the server does not support Version 1.2 . The concrete Faultcode which is returning in the request looks like this: faultactor null faultcode "S:Server" (id=830064966432) faultstring "String index out of range: -11" (id=830064966736) The errorcode which is generated on the server (I'm running it on a localhost) looks like this: 4.05.2010 20:20:29 com.sun.xml.internal.ws.transport.http.HttpAdapter fixQuotesAroundSoapAction WARNUNG: Received WS-I BP non-conformant Unquoted SoapAction HTTP header: http://server.contextlayer.bscwi.de/createContext 24.05.2010 20:20:29 com.sun.xml.internal.ws.server.sei.EndpointMethodHandler invoke SCHWERWIEGEND: String index out of range: -11 java.lang.StringIndexOutOfBoundsException: String index out of range: -11 at java.lang.String.substring(Unknown Source) at de.bscwi.contextlayer.xml.XmlValidator.isValid(XmlValidator.java:41) at de.bscwi.contextlayer.server.ContextWS.createContext(ContextWS.java:45) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.sun.xml.internal.ws.api.server.InstanceResolver$1.invoke(Unknown Source) at com.sun.xml.internal.ws.server.InvokerTube$2.invoke(Unknown Source) at com.sun.xml.internal.ws.server.sei.EndpointMethodHandler.invoke(Unknown Source) at com.sun.xml.internal.ws.server.sei.SEIInvokerTube.processRequest(Unknown Source) at com.sun.xml.internal.ws.api.pipe.Fiber.__doRun(Unknown Source) at com.sun.xml.internal.ws.api.pipe.Fiber._doRun(Unknown Source) at com.sun.xml.internal.ws.api.pipe.Fiber.doRun(Unknown Source) at com.sun.xml.internal.ws.api.pipe.Fiber.runSync(Unknown Source) at com.sun.xml.internal.ws.server.WSEndpointImpl$2.process(Unknown Source) at com.sun.xml.internal.ws.transport.http.HttpAdapter$HttpToolkit.handle(Unknown Source) at com.sun.xml.internal.ws.transport.http.HttpAdapter.handle(Unknown Source) at com.sun.xml.internal.ws.transport.http.server.WSHttpHandler.handleExchange(Unknown Source) at com.sun.xml.internal.ws.transport.http.server.WSHttpHandler.handle(Unknown Source) at com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source) at sun.net.httpserver.AuthFilter.doFilter(Unknown Source) at com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source) at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(Unknown Source) at com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source) at sun.net.httpserver.ServerImpl$Exchange.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) The relevant part of the WSDL (at least that's what I'm thinking) looks like this: <operation name="createContext"> <soap:operation soapAction=""/> - <input> <soap:body use="literal" namespace="http://server.contextlayer.bscwi.de/"/> </input> - <output> <soap:body use="literal" namespace="http://server.contextlayer.bscwi.de/"/> </output> </operation> In my code I'm adding a Header, but it seems like I'm doing it wrong: private static final String SOAP_ACTION = ""; //... SoapSerializationEnvelope soapEnvelope = new SoapSerializationEnvelope (SoapEnvelope.VER11); soapEnvelope.setOutputSoapObject(Request); AndroidHttpTransport aht = new AndroidHttpTransport (URL); //... aht.call(SOAP_ACTION, soapEnvelope); SoapPrimitive resultString = (SoapPrimitive) soapEnvelope.getResponse(); Any advice would be great since I'm running out of ideas.. Thanks folks!

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• Debian and Multipath IO problem

  - by tearman

  Basically the situation is, I have a box running Debian, the box internally has an Intel SCSI RAID controller which is controlling 2 hard drives in RAID1 mode which is where the OS is installed. Further, I have a QLogic fiber channel adapter that connects the unit to a Fiber Channel SAN. My process of installation is I'll install Debian to the local drives, and leave the QLogic firmware out of it for the time being. Then once I get the unit online, I'll install the firmware drivers. This flops my internal drives from /dev/sda to /dev/sdc, which is a bit annoying, but recoverable. Probably should address these by UUID anyways. Once I get back online, I have to install multipath-tools (the framework is a multipath framework). However, once I reboot the machine again, it fails on boot after discovering multipath targets, saying my local drives are busy and cannot be mounted to /root. Any help in what may be the problem here? Or at least how to disable multipath until after the unit boots and then ignores the internal drives?

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• 2 Server FC SAN Configuration

  - by BSte

  I have 2 identical servers: -48GB Ram -8GigE NIC's -2FC NIC's -2x72GB RAID1 Hard Drives -Server 2008R2 Host I also Have a Fibre Channel SAN: -16x146GB RAID10 Hard Drives -2xDual-port FC Controllers (Controller A and B both have ports 1 and 2) -Server 1 has Fiber to Ports A1 and B1 -Server 2 has Fiber to Ports A2 and B2 -I kept the default config with 1 Virtual Disk and 1 Volume -The default mappings show ports A1,A2,B1,B2 on LUN 0 with read-write My goal is: -2xVM's with IIS and Guest Level Failover -2xVM's with SQL 2008 Enterprise using a Single DB and Guest Level Failover -1xVM that is an application server, preferable with Host Failover. From what I read, this will also need AD for clustering to work. -I need at least 1 VM always running for IIS and the SQLDB. This includes hardware failover and application (ie: reboot a VM for Critical updates) I was told I could install the VM's and run them from the SAN, and this is what I've tried: Installed MPIO and HyperV on Server1 and Server 2 Added the SAN as Disk E: on both servers, made it GPT and formatted NTFS Configured HyperV on both server to store use E:\VD and E:\VHD On server1, I was able to install 3 VM's on the SAN and all worked well. On server2, I would start installing the other 2 VM's, but always at some point the VM's would get a corrupt .VHD message (either server). Everything I found about the message typically related to antivirus, so I removed all antivirus on both Host servers (now only running 2008R2). I reformatted drive E: (SAN), recreated the VHD and VD directories, installed 3 VM's on Server 1, and then had the same issue when installing VM's on Server2. Obviously something is wrong, but I'm not certain what exactly. My questions: 1) Are my goals possible with this hardware setup? -I've read 2008R2 supports FC SAN's, but a lot of articles seem to only give examples with iSCSCI setups 2) What would be the suggested route on setting up the SAN (disks,volumes,LUN's)? I've worked with HyperV on a single machine before and never had issues. Actual experience working on SAN's and clustering is new to me. Any suggestions or recommendations to get me in the right direction would be much appreciated.

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• ProCurve network expansion

  - by Blue Warrior NFB

  I've hit a bit of a wall with our network scale-out. As it stands right now: We have five ProCurve 2910al switches connected as above, but with 10GbE connections (two CX4, two fiber). This fully populates the central switch above, there will be no more 10GbE Ethernet connections from that device. This group of switches is not stacked (no stack directive). Sometime in the next two or three months I'll need to add a sixth, and I'm not sure how deep of a hole I'm in. Ideally I'd replace the core switch with something more capable and has more 10GbE ports. However, that's a major outage and that requires special scheduling. The two edge switches connected via fiber have dual-port 10GbE cards in them, so I could physically put another switch on the far end of one of those. I don't know how much of a good or bad idea that would be though. Is that too many segments between end-points? Some config-excerpts: Running configuration: ; J9147A Configuration Editor; Created on release #W.14.49 hostname "REDACTED-SW01" time timezone 120 module 1 type J9147A module 2 type J9008A module 3 type J9149A no stack trunk B1 Trk3 Trunk trunk B2 Trk4 Trunk trunk A1 Trk11 Trunk trunk A2 Trk12 Trunk vlan 15 name "VM-MGMT" untagged Trk2,Trk5,Trk7 ip helper-address 10.1.10.4 ip address 10.1.11.1 255.255.255.0 tagged 37-40,Trk3-Trk4,Trk11-Trk12 jumbo ip proxy-arp exit

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• Hardware, network infrastructure for runnng gaming server nd on VirtualGL

  - by archer

  Foud nice project VirtualGL (http://www.virtualgl.org/). Tried to run 3D fames (EVE Online, Prototype) on server and display the output on thin client using 100Mbps network. Server: Gentoo Linux on AMD Phoenom II x6 3.4Gz, 8GB RAM, 2x NVIDIA 9800 GTX in single session with display resulution 1024x768 on client. Performance is very promising. Going to increase network speed to 1Gbps (using either Ethernet or Fiber) and run 5-6 clients simultenously. My questions are: a) what would be better for network - 1Gbps Ethernet or Fiber (clients are distributed in max 20m around server)? Is that a must to use managed switch for better network performance? b) Should I increase number of video cards to put in SLI on server (going to use Gigabyte GA-890FXA-UD7 which has 6 PCIExpress slots [2 x4, 2 x8 and 2 x16]). Will it impact performance significantly. If I need to increase the number of video cards - what would be better - put 2 banks of video cards with 3 in bank using SLI, or 3 banks with 2 in the bank? Would linux recognize that and properly use all banks of video cards? c) any suggestions on good thin clients supporting 1920x1080 HDMI video and 1Gbps network I understand that my questions can't be answered clearly (unless someone already managed to use this kind of stuff ;)) although any suggestions would be very helpful.

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• sql 2008 disk layout on a budget this is for database mirroring

  - by user22215

  Guys I'm rolling out a SQL database server that will be used to back Sharepoint 2007. Right now I need some advice on my disk layout. I have two Dell servers that are configured a little differently in terms of storage. The principle server will be using a combination of local storage and san storage. I have to work with what I have the organization is currently all allocated on san storage it was like pulling teeth to even get what I have to work with now. My disk setup on the principle is as follows: raid 1 for OS raid 10 for logs raid 10 fiber on san for high IO databases raid 10 sata on san for content databases My question in regards to the principle server is where should I place the temp db? I thought about placing it on the fiber raid 10 which will be hosting my high IO Sharepoint SSP databases my only other choice is to move it to the raid 1 os partition which I’m sure you guys will be against. Now let’s talk about the mirror server it is not connected to the san it is all local 6 15k SAS drives. Now my question is the same do I put tempdb on the os partition or do I leave the os partition and use a single raid 10 for everything? Any help you can provide is much appreciated.

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• Do you really need cable management for a cabinet with just switches and patch panels?

  - by ObligatoryMoniker

  We are about to start wiring out a building expansion and our vendor has laid out the racks in the following configuration: Option 1 1U Fiber patch panel 2U Cable Manager 2U 48 port Patch Panel 2U Cable Manager 2U 48 port Patch Panel 2U Cable Manager 1U 48 port Switch 2U Cable Manager 1U 48 port Switch Total = 15U All the patch panels would be connected to the switches with 1ft+ cables fed through cable management. What I am considering instead is: Option 2 1U Fiber patch panel 1U 24 port Patch Panel 1U 48 port Switch 2U 48 port Patch Panel 1U 48 port Switch 2U 48 port Patch Panel Total = 8U All of the patch panels would be connected to the switches with .5 ft cables directly on their face with the top 24 ports of each switch patched to the patch panel above it and the bottom 24 ports of each switch patched to the patch panel beneath it which would not require any cable management. If I go with option 2 it save all of the space used by cable management and allows us to keep adding on switches and patch panels at the end without having to re-cable all of the patch panels above. Our vendor has indicated that this is not best practice and that .5ft cables will introduce cross talk. I could understand that being the case if we were connecting the .5 ft cable directly into another switch but we are connecting it to a patch panel that likely has another 150 ft cable run from the back of the patch panel out to the port in the building in which case the real resulting cable is 150.5 ft at minimum before even connecting it to a PC. It seems like it makes much more sense to go with option 2. It is easier to expand, saves space, and saves money on cabling and cable management. Does this kind of configuration make sense or is there a legitimate reason to choose Option 1 over Option 2?

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• CentOS Latency High Troubleshooting

  - by Sarah Weinberger

  I have two CentOS servers connected via a 10 Gb fiber optic cable with a network emulator connected between them. All three units sit on a desk in the lab. There is also a regular 1 Gbit Ethernet cable connected to each of the machines, which provide internet connectivity. When I set the latency to something roughly below 30 ms, all is fine. When the latency gets to 70ms and above, and definitely 130ms, the network layer suspends. For instance, if I set the latency (delay) to 70ms, then launching TeamViewer (or any other application that uses network connectivity) never happens or does not work. There is no timeout message, simply no response. I have to lower to latency back down to zero to see any response and have the box start working. What is the problem and how would I go about fixing it? It seems to me some sort of setting in Linux causes one of the CentOS networking drivers to sit in an infinite loop or something. eth0 is the connection to the internet, all settings are default eth2 is the 10 Gbit fiber optic connection to the other computer with the MTU set to 9600 with all other parameters at default values.

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• Stack Managed Switches over a distance

  - by Joel Coel

  We have several buildings with stacked switches, where the distance between the stacked units is considerable... separate floors, or at opposite ends of a hallway. They are 3Com switches that stack using cat6 cabling. These switches are coming up on 12 years old now, and as I look around at replacements it seems no one supports this scenario any more. Stacking switches want to use fiber links (it more for me to run and terminate the fiber stacking cables than to purchase the switch) or other custom cables that seem only intended to jump up to the next unit in a rack. What have others done to support stacking over a distance? I'm considering breaking up the stacked switches into separate managed entities and just bridging from the root switch in the buildings, but I'd really like to avoid that for what I hope are obvious reason. The closest thing I've found are from netgear that use hdmi cables for the stacking connection... I could try to support that by running an additional cat6 line and re-terminating both links into a single hdmi port, but I have concerns over that approach as well.

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• Locate devices within a building

  - by ams0

  The situation: Our company is spread between two floors in a building. Every employee has a laptop (macbook Air or MacbookPro) and an iPhone. We have static DHCP mappings and DNS resolution so every mobile gets a name like employeeiphone.example.com, every macbook air gets a employeelaptop.example.com and every macbook pro gets a employeelaptop.example.com on the Ethernet interface (the wifi gets a dynamic IP from a small range dedicated for the purpose). We know each and every MAC address of phones and laptops, since we do DHCP static mapping (ISC DHCP server runs on linux). At each floor we have a Netgear stack of two switches, connected via 10GB fiber to each other. No VLANs so far. At every floor there are 4 Airport Extreme making a single SSID network with WPA2 authentication. The request: Our CTO wants to know who is present at which floor. My solution (so far): Every switch contains an table listing MAC address and originating port. On each switch stack, all the MAC addresses coming from the other floor are listed as coming on port 48 (the fiber link). So I came up with: 1) Get the table from each switch via SNMP 2) Filter out the ones associated with port 48 3) Grep dhcpd.conf, removing all entries not *laptop and not *iphone 4) Match the two lists for each switch, output in JSON or XML 5) present the results on a dashboard for all to see I wrote it in bash with a lot of awk and sed, it kinda works but I always have for some reason stale entries in the switch lookup tables, making it unreliable; some people may have put their laptop to sleep, their iphones drop connections after a while, if not woken up and so on..I searched left and right, we are prepared to spend a little on the project too (RFIDs?), does anybody do something similar? I can provide with the script if needed (although it's really specific to our switches and naming scheme). Thanks! p.s. perhaps is this a question for stackoverflow? please move if it so.

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• Ethernet switch capacity question

  - by Andrew Queisser

  We're looking at hooking up 48 small embedded systems with 10/100 Ethernet ports to an Ethernet switch and then have that switch talk to a server upstream via a faster connection. I have a couple of questions about that scenario: What kind of upstream connection is best (fiber, other?) Would it be reasonable to download 1GB/hour from each of the 48 systems concurrently? We'd be using some kind of TCP based protocol of our own design. Thanks, Andrew

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• enable Cisco switch to communicate withe HP switch

  - by moosas

  I have one CISCO 2906g and hp 2626 switches i link them by MM fiber optic cable, the problem the cant communicate with each other, i verify there is no problem with cable and JBC's. win i connect other HP switch in the other end it will communicate without any problem, but not with CISCO

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• Need to setup an office network, suggest some hardware?

  - by Yegor

  We have 6 windows workstations, spread out over a fairly large area. Need to share a DSL connection (upgrading to 100/100 mbit fiber in a few months) with these machines over a 1gbit network. Also need Wifi to be available for laptop use. Plan to add 2 rackmount servers for internal use as well. Can someone suggest a decent (preferably low cost) setup that will let me achieve the stuff mentioned above.

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• vSphere 5.5: Binding VMs to HBA cards on the host

  - by red888

  I am settings up a lab and wanted to be sure the following makes sense\is possible: One server running vsphere with two fiber HBAs 2 Windows 2012 Hyper-V VMs each bound to an HBA I'm using vsphere because it supports nested visualization, but I'm really setting up this lab to test out hyper-v and live migrations. Will I easily be able to bind each VM to a physical HBA on the host or are there any caveats I should know about?

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