Search Results

Search found 14292 results on 572 pages for 'high integrity systems'.

Page 459/572 | < Previous Page | 455 456 457 458 459 460 461 462 463 464 465 466  | Next Page >

  • How can I monitor VNC via Nagios?

    - by atroon
    I have a number of remote sites which have VNC running on a few computers for support purposes. They are (obviously) only available on our internal network. I am using Nagios to keep track of all the systems in the network and I want to have it check to make sure the VNC server is running on the appropriate hosts. There is a 'check_vnc' plugin available here but it relies on VNC Snapshot which I don't want to use. Certainly I could use it, but it adds more complexity and dependency, which I want to avoid. It seems simpler to just use check_tcp to make sure I get the proper response to a connection request for VNC, e.g. port 5900, send a connect string, get back framebuffer info. My real question, I suppose, is this: What is the 'proper' generic connect string for VNC (I use both UltraVNC and RealVNC) and what is the expected response? If it's really easier to use the VNC Snapshot and check_vnc, let me know. I just can't imagine that a string of text isn't easier, faster, and less bandwidth intensive to monitor.

    Read the article

  • i7 Windows 7 laptop or Macbook Pro 15" (For making 3D model and Animation)

    - by sppdhs
    Hi everyone, I'm thinking of buying a new laptop as my current one will be 5 years old next year and it currently gives me a blue screen everytime I run a heavy software to make 3D models and animation. Question is: Should I buy Macbook Pro or a Windows 7 laptop? I tried to research and some say that Windows would be better, especially because you can buy a very high spec laptop with cheaper price. While some other say Macbook Pro is the better choice as it can run bootcamp with windows 7 100% performance on every software even though it's a mac. Is this true? Which one is actually better? Btw, the software that I usually use is 3Ds Max, Maya, and ZBrush. To note as well, I have never used a Mac before. I've checked around some stores and budget wise, I'll need around AU$3000+ to buy a Macbook pro, and AU$2000+ to buy a windows laptop. Quite a big difference in price range. Thanks in advance for your help.

    Read the article

  • using i7 "gamer" cpu in a HPC cluster

    - by user1219721
    I'm running WRF weather model. That's a ram intensive, highly parallel application. I need to build a HPC cluster for that. I use 10GB infiniband interconnect. WRF doesn't depends of core count, but on memory bandwidth. That's why a core i7 3820 or 3930K performs better than high-grade xeons E5-2600 or E7 Seems like universities uses xeon E5-2670 for WRF. It costs about $1500. Spec2006 fp_rates WRF bench shows $580 i7 3930K performs the same with 1600MHz RAM. What's interesting is that i7 can handle up to 2400MHz ram, doing a great performance increase for WRF. Then it really outperforms the xeon. Power comsumption is a bit higher, but still less than 20€ a year. Even including additional part I'll need (PSU, infiniband, case), the i7 way is still 700 €/cpu cheaper than Xeon. So, is it ok to use "gamer" hardware in a HPC cluster ? or should I do it pro with xeon ? (This is not a critical application. I can handle downtime. I think I don't need ECC?)

    Read the article

  • file system that allow to specify different RAID level per directory and change it afterward

    - by Adam Ryczkowski
    I have 5 hard drives, where I want to keep my data. Some of my files are more important, and some of them are less. So some of them I wish to put on RAID-6, and for some it RAID-5 is sufficient. It is difficult to predict at the moment of creation of the arrays how much space of each type to declare. What I would do if I didn't hear about zfs, is partition the hard drives into identical 100GB partitions, and as my needs grow, assemble those partitions into md devices using linux-raid. Then, I'd combine those devices using lvm into logical volumes where I'd put my data. So when I'd need more space of e.g. RAID-6, I'd take 100GB partition from each hard drive and assemble them into another RAID-6 md device and would use it as physical storage for the logical volume group dedicated for RAID-6 data. Then I could grow the file system on this logical volume. On top of RAID-6 and RAID-5 Volume Groups (managed by lvm) would reside completely independent file systems, which I'd later merge with multiple mount --bind into a single directory structure that would reflect the logical structure of data rather that of the storage. But now, when I heard about the ZFS with all the performance, data-healing and compression capabilities I cannot stop thinking if it can help me. If so, what do you think would be the best setup?

    Read the article

  • Can't mount Linux usb disk. It just create /dev/sg device but no /dev/sd

    - by MTilsted
    I have a Corsair R60 ssd disk which is a disk with both sata and usb connectors. But the usb thing seems to be a bit non-standard, or maybe its just my fedora linux. When I insert the disk using a usb cabel to a running Fedora 14 linux system, a device called /dev/sg3 is added but that is all. No new /dev/sd* device is created so I can't mount the disk. If I look at cat /proc/scsi/sg/device_strs I get ATA Hitachi HTS54321 FB2O HL-DT-ST DVDRAM GSA-T50N RP05 Seagate Desktop 0130 Corsair CSSD-R60GB2 So the disk is there. (The last entry) but my linux will for some reason not see it as a usb hard disk. When I insert other usb disks they work fine. It is only this specific disk which causes problems. I have tried on 3 different computers with the same result. A hint to the problem may be that if I add the disk to a windows system(With usb) the disk is called "A fixed disk" and not a portable disk as expected. The disk works fine with linux If i connect it with the sata cabel, but I would really like to have it working with usb too. (To mount it on computers without sata). Added: I did try to mount /dev/sg3 but mount say that its not a block device. (File say Its a character special device). Added output from dmesg: [ 97.454073] usb 7-1: USB disconnect, address 2 [ 105.913055] hub 2-0:1.0: unable to enumerate USB device on port 3 [ 107.048054] usb 2-3: new high speed USB device using ehci_hcd and address 5 [ 107.162900] usb 2-3: New USB device found, idVendor=1b1c, idProduct=1ab8 [ 107.162903] usb 2-3: New USB device strings: Mfr=1, Product=2, SerialNumber=5 [ 107.162906] usb 2-3: Product: CSSD-R60GB2 [ 107.162908] usb 2-3: Manufacturer: Corsair [ 107.162910] usb 2-3: SerialNumber: 10111441000000990069 [ 107.167651] scsi7 : usb-storage 2-3:1.0 [ 108.195543] scsi 7:0:0:0: Direct-Access Corsair CSSD-R60GB2 PQ: 1 ANSI: 0 [ 108.197732] scsi 7:0:0:0: Attached scsi generic sg3 type 0

    Read the article

  • Help, my CentOS servers keep going down , No route to host after a random uptime

    - by user249071
    Hello , I have a couple of Centos linux servers, that have a very simple task, they run nginx + fastcgi for php , and some NFS mounts between them, readonly They have some RPC commands to start some downloading processes with wget, nothing fancy , from a main server, but their behavior is very unstable, they simply go down, we tried to monitor ram , processor usage, even network connections, they don't load up so much, max network connections up to... 250 max, 15% processor usage and memory , well, doesn't even fill up, 2.5GB from 8GB max , I have no ideea why can a linux server go down like that, they aren't even public servers, no domain names installed no public serving, for sites. The only thing that I've discovered was that if i didn't restart the network service every couple of hours or so... the servers were becoming very slow, starting apps very slow, but not repoting a high usage of resources...Maybe Centos doesn't free the timeout connections, or something like that...It's based on Red Hat right? I'm not a linux expert , but I'm sure that there are a few guys out there that can easily have an answer to this , or even have some leads to what i can do ... I haven't installed snort, or other things to view if we have some DOS attacks, still the scheduled script that restarts the network each hour should put the system back online, and it doesn't.... Thank you in advance

    Read the article

  • How to manage unprivileged administration of system services using Debian?

    - by ypnos
    At our lab, we have several services handled by different phd students (like myself). Fluctuation is high and people do the job next to their research duties. Until now, services were running on different machines, with different OS setups that can result in administration hell quickly. We want to consolidate our service setup. Our main idea is that the guys responsible for the services should not meddle with the underlying system anymore. Apart from core systems like NFS and kerberos, a typical service is able to run as non-root already. I'm talking about apache, mysql, subversion, mail with openxchange, and so on. Redirecting privileged ports is also no issue (source). What is left is the configuration of the service and its payload. One scenario we envisioned is that every service has its own user and home directory, accessable by the corresponding admins. Backup and fallback of the service is easy, as everything needed for the service to run is found in one place. Are there established ways to create such a setup? Does a mostly unique method exist to make services find their files (other than in system directories) while still using the corresponding debian packages? Are there any catches with our idea that we may have overlooked? Would you maybe claim that virtualization is the answer to our problem? (In our POV, it wouldn't help us keeping system setup strictly separated from service setup.) Thank you for any advice!

    Read the article

  • How to set an executable white list?

    - by izabera
    Under Linux, is it possible to set a white-list of executables for a certain group of users? I need them to be unable to use, for example, make, gcc and executables on removable disks. How can this be done? Edit, let me explain better. I'm dealing with a high school IT system, young geeks that (during the lessons) want to play, surf the net, damage those computer however they can. The major step to achieve this goal was to remove the system they're familiar with and install Ubuntu in all the computers. This actually works quite well, but recent events proved that this is not enough. I want to allow them to execute certain safe programs, like Open Office, and to deny any other program, whether it is preinstalled software, something they carry in usb drives, a downloaded program or a script they program on site. It's possible to remove the 'x' permission on any file on the pc, but of course it would be impractical. Furthermore, they would be able to run anything they download. I thought the best solution would be to make a white-list of safe programs and to deny anything else, but I don't really know how to do it. Any idea is helpful.

    Read the article

  • Standing and sitting while using a computer at work

    - by Adam Batkin
    I would like to be able to comfortably switch between sitting and standing while at work (I'm a software developer, so I spend most of my day in front of a computer). For the past couple of months I have been using a large elevated stand that sits on my desk (designed expressly for this purpose) containing my keyboard and mouse, and my monitors have been raised as high as possible and aimed upwards. So I can stand all day and I'm pretty comfortable (my right wrist may be at too much of an angle when it's on my mouse, but that's a separate issue). The only problem is that sometimes I want to be able to sit. I can easily place my keyboard and mouse back down under the elevated stand, but I have to look up pretty steeply and that is uncomfortable and makes it difficult to see the screens since they are tilted upwards. My monitor mounts are difficult to adjust quickly/easily, so I can't just re-aim them. I would of course love one of those hydraulic standing/sitting desks (cost isn't the problem). But I'm in a row of "trader-style" desks where it's basically a very long surface with people sitting at 6-foot intervals. What type of equipment do you recommend? I suppose the best thing would be some sort of monitor stand (it must be able to hold 2-3 LCDs) that can easily be lowered and raised. But any other suggestions are also welcome.

    Read the article

  • Toshiba A205-5804 freezes when plugged in

    - by heron
    Well I have a Toshiba A205-5804 and the problem is that the screen freezes anytime I plug the pc into the external power supply, not as most of the computers having the same issue, my computer DOES freeze in safe mode, and I really can't bear this problem for much longer... It's not an overheating problem, the computer is not getting hot or anything related, I've already tried changing the AC adapter, booting only with AC and no battery, and also all of these suggestions: Try changing the following setting in the bios setup, under the 'Advanced' tab Dynamic CPU Frequency: Mode = Always Low (NOT DYNAMIC) My laptop has been running on AC power without a problem for 24hours, including many restarts, and when I went back to the original bios setting, the problem returned almost straight away. EDIT Other suggestions I found on the web from here and here: Set the power plan to high performance Set the power plan to "Minimal Power Management" (1 and 2 do conflict) Start - Control Panel - Device Manager -- Processor - disable one of two processors - reboot normally 4.Do this: Only plug battery into laptop Turn on the laptop and start Windows normally Plug AC adapter into laptop, the screen will freeze Leave the laptop the way it is for 12-24 hours After 12-24 hours, turn it off the hard way Once it is turned off, turn it back on. The laptop is working now. I have no idea of what can it be...

    Read the article

  • EC2 Auto-Scaling with Spot and On-Demand Instances?

    - by platforms
    I'm looking to optimize the cost of our auto-scaling EC2 groups by having them launch spot instances instead of on-demand instances. What I really want is to be able to keep some servers in the group as on-demand instances, regardless of what happens to the spot instance pricing market. Then I want any additional servers in the group, above my configured minimum, to be spot instances. I'm generally OK with the delay in adding servers via spot requests. I can't seem to find any way to do this and I've tried to scour the AWS documentation. It appears that an ASG can either be on-demand or spot, but not a hybrid. I could possibly manually add an on-demand instance to the Elastic Load Balancer assigned to the auto-scaling group, but then the load of that server would not be factored into the auto-scaling measurements and triggers. I suppose I could enter a ridiculously high bid price in order to ensure that I always get the servers I need, but then I look at the pricing history and see occasional large spikes. The AWS documentation is at odds with itself, since in one place it says that if you enter a server minimum, that number is "ensured" to be there. But then when you read about spot instances, there are no assurances. The price differential for spot is compelling, so I'd like to leverage that as much as I can while still maintaining an always-on baseline. Is this possible?

    Read the article

  • Disk Activity Alert Windows SBS 2003 on Dell PowerEdge 830 with Raid

    - by Ron Whites
    Background: I have a Dell PowerEdge 830 Server running Windows SB Server 2003. It has 4gbs of RAM and a ATA CERC SATA 6CH controller with 3 160gb drives in a Raid 5 configuration. The Problem I am seeing Admin ---"Disk Activity Alert on Server" emails These often occur when disk backups, de-frag or high disk usage is going on. Generally the server isn't over stressed. The Disk Alert emails say in part ... The following disk has low idle time, which may cause slow response time when reading or writing files to the disk. Disk: 0 C: F: D: Review the Disk Transfers/sec and % Idle Time counters for the PhysicalDisk performance object. If the Disk Transfers/sec counter is consistently below 150 while the % Idle Time counter remains very low (close to 0), there may be a problem with the disk driver or hardware. The Questions I have: With what utility can I review the Disk Transfers/sec and Idle Time? It appears there is no utility for that on the server! I think I may need to download a very large (two DVD) Dell "OpenManage" utility to be able to monitor the raid system and see what is a problem is that true?

    Read the article

  • Encrypted Windows 7 & Linux Advice Wanted

    - by Miles
    I would like to set up my laptop to dual boot Arch Linux and Windows 7 with file sharing and encryption. Just wanted some advice on going about this because I have not dealt with encryption nor file sharing. I have two 500GB hard drives, and this is my plan: Install Windows 7 across both hard drives Use a live CD to wipe out Windows boot loader and replace with Grub Legacy Use live CD to wipe out second hard drive and re-size the Windows partition located on first hard drive Install Arch Linux along side with Windows 7 on first hard drive, all remaining space goes to home folder as ext2 Install truecrypt and ext2fsd Concerns: Is this the most efficient way to share files between both OSes? Or should I just be using NTFS to store all my data? How would the file permissions work when sharing files between Windows and Linux? Is there a high likley hood of corruption, and what is the ease of backing up files from an encrypted disk? Anything I should look out for, conflict between Grub and Truecrypt? Thank you for any advice, and feel free to post any links you might find useful to me. I am trying to plan this out so I can minimize downtime as I do not want to spend more than a night on this, nor do I want to run into a major problem some time in the future.

    Read the article

  • Recommended Smartphone for Reading PDFs [closed]

    - by mika
    This is as much a software than a hardware question. I use a lot of public transport and perhaps the best way to spend your time there is to read while listening to music. Currently I use Nokia E90 and Adobe Reader LE 2.5 (full version). I was wondering if there are any better alternatives? Requirements: at least 640px wide screen, preferably 800px physical size of the LCD display matters, it should be large, but the phone itself should be as small as possible. This favors touchscreen models PDF reader should be of high quality. It should render most PDFs correctly. Other important features include: full screen mode, keyboard controls for Page Down and page change, multiple zoom levels to adjust to the screen, opening recent documents at the last page read Downsides of E90 + Adobe Reader LE Phone is large compared to the display It is hard to read the display at sunlight Adobe Reader crashes the phone regularly, zoom could have more levels, doesn't remember last page EDIT: Switched to iPhone and GoodReader. Smaller physical screen width compared to E90 is a disimprovement, but other than that I'm happy. GoodReader is the highest quality smartphone PDF reader I've seen so far.

    Read the article

  • Custom PCI bracket with support, for custom PCB?

    - by newbiez
    I am considering to put a custom PCB card that I made, into my computer. It won't go on any PCI connector, it plugs in on a USB connector on the motherboard, via a ribbon cable. I need thou to plug a device to it; which means that either I leave the PCB outside the case, hanging by the ribbon (bad idea), or I could put it in a PCI slot, using a bracket. The issue is that the brackets that I have, do not have tabs, so I have no way to screw the PCB on them. I was hoping to find something that would allow me to put the PCB on it, and then just fit it in the PCI bracket opening, like this: http://www.idotpc.com/TheStore/pc/viewPrd.asp?idproduct=1203&idcategory=0 This one won't fit the bill since the holes are too close apart, compared to the one that I have already on the PCB (and can't make more holes). Do you know if there is a place where they make universal PCI bracket mounting systems for custom PCB? I just need one, so can't even order a custom one (they ask me 120 dollars for one). Thanks in advance!

    Read the article

  • Network Security Device/Software

    - by Campo
    We currently run Symantec Antivirus Corporate 10.2. The software is really easy to manage on a network but the actual virus detection isn't bad but the malware detection is crap. We recently were infected with a email bot that got us put on some block lists. This has been resolved. I cannot have that happen again. I would like to find a program as easy to manage as symantec that I can install on all the user's workstations as well as the servers. We run a windows 2003 domain. We have a couple 2008 test servers in the environment. Most of the workstations are xp though I am using windows 7 and symantect is not compatible with this OS... So we need a solution that would cover all those operating systems. If it could be installed on macs too that would be a bonus though not necessary at all. This software must detect: Viruses AND Malware I am looking for something that combines the features in anti-malware programs like malwarebytes or spybot with an antivirus program like symantec or AVG. Alternatively if there is a piece of hardware that is a firewall, router, and packet inspection for virus/spam that would be the most ideal solution. I then could supplement with a piece of software that could pickup what the hardware misses. Thank you for your suggestions.

    Read the article

  • Hearing a clicking noise from soundcard all the time

    - by Mehrdad
    I have installed Fedora 17 on my laptop. A few days ago I updated my fedora (but not upgraded). I shut down my computer and since the next time I turned it on I am hearing a clicking noise all the time from speakers. Even when I plug my headphones in I hear the noise through the headphone. I surfed over the internet and found the following shell commands: su -c 'echo "options snd_hda_intel power_save=0" /etc/modprobe.d/snd_hda_intel.conf' su -c 'echo 0 /sys/module/snd_hda_intel/parameters/power_save' I tried them but they didn't work. Here is the part of "lspci" command related to my sound-card: 00:1b.0 Audio device: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) High Definition Audio Controller (rev 03) I have to add that my sound-card is working and I can play some audio file, I mean I can hear the voice and noise simultaneously. But everything is OK in windows xp which is also installed on my laptop. Could it be related to the sound-card driver? If so, how can I revert it to the previous version?

    Read the article

  • Developer hardware autonomy in a managed desktop environment [closed]

    - by Troy Hunt
    I’m looking for some feedback on how developer PCs are managed within environments that have a strict managed desktop policy (normally large corporations). For example, many corporate environments control the installation of software and the deployment of patches and virus updates through a centralised channel. This usually means also dictating the OS version and architecture (32 bit versus 64 bit) which will likely also mean standardised hardware configurations. I’m particularly interested in feedback from developers who work in this sort of environment but have a high degree of autonomy over their machines. This might mean choosing your own hardware vendor, OS type and version and perhaps how the machines are built and maintained. I have several specific questions: How do you satisfy the needs of security, governance etc whilst maintaining your autonomy? For example, how do you address concerns about keeping virus definitions and OS patches up to date? Do you have a process for gaining exemption from standard desktop builds and if so, what do you need to demonstrate in order to get this? How have you justified this need to the decision makers? Essentially, what is the benefit to your role as a developer by having this degree of autonomy? Thanks very much everyone. Update: There's a great post from Jean-Paul Boodhoo which addresses the developer tool component of the quesiton here: http://blog.jpboodhoo.com/TheFallacyOfTheStandardizedDeveloperMachineimage.aspx

    Read the article

  • Nagios DNX plugins

    - by danneh3826
    I'm toying with the idea of multiple Nagios instances setup to monitor our infrastructure. I've looked at all the various methods of distributed Nagios checks, and I think DNX comes out the closest. DNX handles failure of worker nodes, that's fine. What happens if the main DNX server fails though? Is there a way to replicate the server too? I'm using AWS EC2 primarily, so I can utilise Elastic Load Balancing for the web UI, but I need to be able to handle the AZ where the monitoring server is to fail over, and essentially for a second to pick up the checking load (active/passive, active/active, so long as it doesn't fail completely) The other thing I'm trying to solve is an issue with routing. What I'd like is to have multiple nodes report a fault before Nagios confirms it as critical. Not the NRPE checks, as they're pretty self explanitory, but things more like check_ping. I often have routing issues out of AWS to certain datacenters, so Nagios can often report bad/no ping/timeout as a critical issue, even though the machine in question is working fine. Would it be possible to have a setup where a worker complains a service check is critical, and have a second worker node (positioned in another datacenter/AZ) also report the service as critical before the Nagios central server issues a critical alert? I realise I might be asking a bit much (how far down the line do you go setting up failover systems before it starts to get ridiculous), however surely someone must have thought of this scenario when developing DNX?

    Read the article

  • How to monitor bandwidth use of each device on wifi network

    - by GWLlosa
    I have in my home a standard Comcast cable internet connection. I have it going from the wall to a cable modem, and from the modem to a late-series Linksys router, which provides wired and wireless networking. The vast majority of the users are wireless connections. For day-to-day tasks, this connection is fully sufficient for all my needs. However, on regular occassions, we have social gatherings that involve many people bringing laptops and other PCs and using the network and internet simultaneously, frequently for gaming. I have no administrative oversight over these machines; they have been known to be riddled with spyware and/or bloatware or be running torrents, legal or otherwise. The only reason I care is that on a regular basis, one of the machines will flatline my internet bandwith, and consume it all in order to upload/download/spam people/whatever. When this happens, the latency of the connections for gaming and the like becomes unacceptable, and everyone suffers. My question is: Is there a system I can set up whereby I can easily monitor the various systems connected to my wireless connection, see how much bandwith each one is using, and for what ends? That way, at a glance, I can spot the offending machine and kick it from the connection, without having to go from machine to machine, checking each one's "bandwith used" properties manually, and dealing with the owner's indignant protests all the while. I understand this will likely involve 3rd-party software and/or hardware; my issue is I don't even know where to begin.

    Read the article

  • Determine from where is "sh" being run under apache www-data user using using PF or NETSTAT

    - by Eugene van der Merwe
    I am working with a compromised Ubuntu 8.04 Plesk 9.5.4 server. It seems that a script on the server is continuously doing reverse lookups to random IPs on the Internet. I first spotted it during by using top and then noticed flashes of this coming up continuously: sh -c host -W 1 '198.204.241.10' I wrote a this script to interrogate ps every 1 second to see how frequently this script happens: #!/bin/bash while : do ps -ef | egrep -i "sh -c host" sleep 1 done The results are that this script runs often, every few seconds: www-data 17762 8332 1 10:07 ? 00:00:00 sh -c host -W 1 '59.58.139.134' www-data 17772 8332 1 10:07 ? 00:00:00 sh -c host -W 1 '59.58.139.134' www-data 17879 17869 0 10:07 ? 00:00:00 sh -c host -W 1 '198.204.241.10' www-data 17879 17869 1 10:07 ? 00:00:00 sh -c host -W 1 '198.204.241.10' www-data 17879 17869 0 10:07 ? 00:00:00 sh -c host -W 1 '198.204.241.10' root 18031 17756 0 10:07 pts/2 00:00:00 egrep -i sh -c host www-data 18078 16704 0 10:07 ? 00:00:00 sh -c host -W 1 '59.58.139.134' www-data 18125 17996 0 10:07 ? 00:00:00 sh -c host -W 1 '91.124.51.65' root 18131 17756 0 10:07 pts/2 00:00:00 egrep -i sh -c host www-data 18137 17869 0 10:07 ? 00:00:00 sh -c host -W 1 '198.204.241.10' www-data 18137 17869 1 10:07 ? 00:00:00 sh -c host -W 1 '198.204.241.10' My theory is if I can see who is launching the sh process or form where it's launched I can isolate the problem further. Can somebody please guide me using netstat or ps to identify from where sh is being run? I might get many suggestions that the OS is out of date and so the Plesk, but please bear in mind there are some very concrete reasons why this server is running legacy software. My question is aimed at a advanced Linux systems administrators who have in depth experience with security compromises and using netstat and ps to get to the bottom of it.

    Read the article

  • Outdoor WiFi Mesh Topology vs. Repeaters

    - by IronJaxor
    Here's the current configuration in our organization (which I believe is incorrect): We have a number of Cisco 1500 series AP's (22 in total), that are mounted outdoors to provide seamless WiFi coverage over a large area. Each AP however has its own physical ethernet connection back to the WLC (All the AP's are marked as Root AP's). They are all broadcasting the same SSID. We have tried to stagger the channel selection but because there are only three non-overlapping channels to choose from, and in some areas the density of AP's is quite high, there is multiple places of channel interference. With this configuration we experience 100-150 disconnects from clients every day. (Our clients are mobile so they move throughout the coverage area constantly). My idea is to switch the AP's to the same channel thereby forming a wireless mesh, use the built in functionality of the 1500 series to use 802.11a as the backhaul, designate one or two AP's as root AP's and wire them back to the WLC. Thereby forming a WiFi mesh, which if I'm not mistaken is the point of the 1500 series in the first place! I am however completely new at WiFi networks and wondering if I am simply mistaken in what I believe my proposed changes will enable, or if there is a better way to tackle the WiFi topology.

    Read the article

  • Linux iptables / conntrack performance issue

    - by tim
    I have a test-setup in the lab with 4 machines: 2 old P4 machines (t1, t2) 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t3) Intel e1000 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t4) Intel e1000 to test linux firewall performance since we got bitten by a number of syn-flood attacks in the last months. All machines run Ubuntu 12.04 64bit. t1, t2, t3 are interconnected through an 1GB/s switch, t4 is connected to t3 via an extra interface. So t3 simulates the firewall, t4 is the target, t1,t2 play the attackers generating a packetstorm thorugh (192.168.4.199 is t4): hping3 -I eth1 --rand-source --syn --flood 192.168.4.199 -p 80 t4 drops all incoming packets to avoid confusion with gateways, performance issues of t4 etc. I watch the packet stats in iptraf. I have configured the firewall (t3) as follows: stock 3.2.0-31-generic #50-Ubuntu SMP kernel rhash_entries=33554432 as kernel parameter sysctl as follows: net.ipv4.ip_forward = 1 net.ipv4.route.gc_elasticity = 2 net.ipv4.route.gc_timeout = 1 net.ipv4.route.gc_interval = 5 net.ipv4.route.gc_min_interval_ms = 500 net.ipv4.route.gc_thresh = 2000000 net.ipv4.route.max_size = 20000000 (I have tweaked a lot to keep t3 running when t1+t2 are sending as many packets as possible). The result of this efforts are somewhat odd: t1+t2 manage to send each about 200k packets/s. t4 in the best case sees aroung 200k in total so half of the packets are lost. t3 is nearly unusable on console though packets are flowing through it (high numbers of soft-irqs) the route cache garbage collector is no way near to being predictable and in the default setting overwhelmed by very few packets/s (<50k packets/s) activating stateful iptables rules makes the packet rate arriving on t4 drop to around 100k packets/s, efectively losing more than 75% of the packets And this - here is my main concern - with two old P4 machines sending as many packets as they can - which means nearly everyone on the net should be capable of this. So here goes my question: Did I overlook some importand point in the config or in my test setup? Are there any alternatives for building firewall system especially on smp systems?

    Read the article

  • Is it a good Idea to switch to a SSD to use less battery?

    - by Walter Maier-Murdnelch
    I am thinking of buying a SSD for my laptop, mainly for the purpose of extended operating time when running on battery. At the moment I use a Hitachi HTS545032B9A300 (320GB) (Datasheet) as main drive and a Seagate Momentus 5400.3 120GB as secondary drive. I dualboot Windows and Linux but I don't need the windows partition any longer, a 120GB SDD would be more than sufficient space-wise. Speed is not an issue for me, I make heavy use of tmpfs (ramdrive) within Linux and transfers of bigger files are mainly through some network filesystem anyways, thus a cheaper SSD should do. For the purpose of comparison I chose the OCZ Vertex Plus 120GB. Power consumption always is a big promotional thing the industry uses to make me want to buy their SSDs, some sheet on the OCZ page provides an astonishing comparison of desktop HDDS and SSDs. The numbers I got comparing my laptop HDD and their SSD were not really astonishing any longer. Hitachi 320GB HDD: Startup (W, peak, max.) 4.5 Seek (W, avg.) 1.7 Read / Write (W, avg.) 1.4 Performance idle (W, avg.) 1.3 Active idle (W, avg.) 0.8 Low power idle (W, avg.) 0.5 Standby (W, avg.) 0.2 Sleep 0.1 OCZ 120GB SSD: 1.5W active 0.3W standby I see that there are differences, but actually they don't seem that high as I though they were. And compared to the power consuption of the rest of my system I wonder if it makes a difference at all. Have I just taken the wrong look at the whole thing or may I be better off to buy another battery for my laptop?

    Read the article

  • Video card not detected in POST on initial boot.

    - by Jeff M
    I have a minor problem with my desktop computer after cleaning it out for dust. When I first boot up the computer, the video card does not get detected so I can't see anything. In POST, I'm getting the "can't detect video card" beeps. The boot sequence continues normally, just without video. However, if I restart it (using the restart button) anytime after POST, it would boot up normally. I have no reason to think that the motherboard, video card or PSU got damaged in the process. It was working fine before, works fine after resetting. Took all the necessary precautions while cleaning. On the initial boot, I can hear the video card's fan power up but immediately power down and try again one more time only to fail. After the beep, resetting gets everything running and sounding normally. I've reseated the card a couple of times and reset the BIOS but doesn't seem to help. I'm hoping I won't have to take it out and remove and reinstall everything again. Does anyone recognize these symptoms to know exactly what the problem is? My guess is that the video card isn't getting enough juice initially to be running stable to be detected. I just don't know what I did (or didn't do) to get it to be in this state. It's not a high priority thing for me at the moment, just means I have to always reset it after initially turning it on but will eventually remove everything and reinstall if it comes to that. I don't think the specs are relevant here but just in case, here's the relevant stuff: Motherboard: Gigabyte P35-DS3P Video: EVGA GeForce 8600 GTS PSU: Antec True Power Trio 650W Built ~2 years ago, still running well

    Read the article

< Previous Page | 455 456 457 458 459 460 461 462 463 464 465 466  | Next Page >