• How Does Cisco CUCM (Cisco Unified Communication Manager) Work?


    Cisco's CUCM (Cisco Unified Communication Manager) is a system that combines voice, video, data and mobile products into a single unified management suite. At its core, the CUCMis like a "Super PBX" that controls the flow of all communications through an organization even single or multiple site deployments. Cisco's CUCMmakes communication more effective and simple through centralized management and unification of communications resources.........
  • USB 3.0 PCI x1 Card Review VIA VL805 on Linux Review and Experience


    This is a VIA made VL805 USB 3.0 Chipset with 4-ports and MOLEX powered. First of all this unit was cheap at about only 9 USD with fast shipping. My biggest concern was if this was a quality unit and would it really give you full USB 3.0 speeds (some people reported with similar cards that for some weird r........
  • mdadm mirrored RAID1 performance using RAID10 -f2 (Far Layout) is the solution


    The only way I've found in mdadm to make 2 drives perform like a proper RAID 1 (eg. the read speed should be 2x that of a single drive) is to use the --layout=f2 (far 2). mdadm raid10 performance issues. Be very aware that mdadm seems to default to layout=n2 (which means near). In this scenario it means it is like mdadm RAID 1 performance (you get maximum read speeds of a single drive). dd if=/dev/md126 of=/dev/null bs=1M cou........
  • HP Procurve Switch 2824 CLI Telnet Experience , Guide and Tutorial


    telnet 192.168.1.54 ------------------------------------- ProCurve J4903A Switch 2824 Software revision I.10.77 Copyright (C) 1991-2009 Hewlett-Packard Co. All Rights Reserved. RESTRICTED RIGHTS LEGEND Use, duplication, or disclosure by the Government is subject........
  • VPN Account Buyers Guide and General Info


    What does VPN stand for? VPN stands for Virtual Private Network and is a secure way of connecting networks and devices. In the context we're talking about it will usually be a client-server solution and not connecting whole networks or businesses. The assumption is that most people reading this are trying to secure their internet connection, privacy and hide or change their IPaddress. Why use a VPN? There are many........
  • CPanel Apache httpd won't start solution: Starting httpd: Syntax error on line 2 of /etc/httpd/conf/httpd.conf: Invalid command 'Alias', perhaps misspelled or defined by a module not included in the server configuration


    root@hkhosting [/]# service httpd start Starting httpd: Syntax error on line 2 of /etc/httpd/conf/httpd.conf: Invalid command 'Alias', perhaps misspelled or defined by a module not included in the server configuration ........
  • Are my WDEARS20 Drives dying already?


    This happened during a RAID array check: SMART says both drives pass the test, but I'm doing a long test on them and hopefully this is not a hardware error. Apr 3 04:22:01 remote kernel: md: syncing RAID array md2 Apr 3 04:22:01 remote kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc. Apr 3 04:22:01 remote kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction. Apr........
  • Linux High IOWAIT updatedb can't be killed and crash with mdadm


    high IO wait 424 root 39 19 1900 848 552 D 0.0 0.0 0:00.91 updatedb root 424 0.0 0.0 1900 848 ? DN Mar11 0:00 /usr/bin/updatedb -f sysfs?rootfs?bdev?proc?cpuset?binfmt_misc?debugfs?sockfs?usbfs?pipefs?anon_inodefs?futexfs?tmpfs?inotifyfs?eventp........
  • 95th Percentile Billing vs Usage Billing, what's better?


    There are all kinds of threads and links on the internet, and this seems to be a contentious issue butI don't know why. 95th percentile is either a good deal for some or a big rip off for others, Ijust said it there :) But the reality is that for MOST people who transfer low amounts of data but burst to higher speeds such as 40mbit+ even for short periods of time, then you'll pay a lot of money to do that. Basically 95th percentile is an-old archaic method........
  • CPU #1 not responding - cannot use it.


    I think this will be useful to others because I have a server that kept crashing mysteriously during intense disk usage/RAID checks. It would only crash during the weekly RAID integrity check. ThenI noticed during a reboot that not all CPUs were being brought up, as a result this actually creates much higher temperatures with the output I got from sensors, just booting the system produced higher than normal temperatures. You can imagine that a full blown RAID check........
  • updatedb/mdadm caused a kernel panic?


    Jan 16 04:02:03 centosbox syslogd 1.4.1: restart. Jan 16 04:07:34 centosbox kernel: INFO: task updatedb:20771 blocked for more than 300 seconds. Jan 16 04:07:34 centosbox kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Jan 16 04:07:34 centosbox kernel: updatedb D F78BE050 6476 20771 20766&n........
  • mdadm Centos 5 automatic resync


    This made me nervous but it's clearly a cronjob based on the messages log that happens every Sunday at about 4:22. I actually can't find any evidence of it in cron.d cron.daily but it is there somewhere obviously. What I don't get is why doesn't this cronjob do a datacheck like Ubuntu's cronscript does? When you unnecessarily rebuild the array you lose your redundancy during that point which makes your data extremely vulnerable. *Update I did a grep of &q........
  • mdadm/md-check how to check array integrity without rebuilding


    This doesn't seem to be widely known (maybe it's in some documentation that none of us read though)but there's an easy way to check the integrity of any mdadm array: sudo echo check > /sys/block/md0/md/sync_action -bash: /sys/block/md0/md/sync_action: Permission denied sudo will never work, this only works as root since echo is not actually a binary/command. It is built-into bash. /sys/devices/virtu........
  • md: data-check of RAID array md3


    This really made me nervous but notice the mdstat says "check". This is because in Ubuntu there is a scheduled mdadm cronscript that runs everyday on Sunday at 00:57 that checks your entire array. This is a good way because it prevents gradual but unnoticed data corruption which Inever thought of. As long as the check completes properly you have peace of mind knowing that your data integretiy is assured and that your hard drives are functioning properly (I'........
  • Monitor MB/s Disk IO Usage/Bandwidth - Use iostat from the sysstat Package


    The binary "iostat" comes from the package "sysstat" and is available on all Linux/Unix like platforms. Use the "-m" option to give you what you probably want, which is to see in MB/s how much bandwidth each disk is doing. iostat -m Linux 2.6.24.2 ((none)) 04/16/10 avg-cpu: %user %nice %system %iowait %steal %idle ........
  • OpenVZ backup container to a single file while it's running using "vzdump"


    Proxmox has made this free utility to backup running OpenVZ containers. It's a great program which is actually just a PERL script but gets the job done. This program is not 100% required because all it really does is cp -a from your container's path as far as I know but it is still good to have uniformity to how you backup your containers. For RPM distros such as Centos/RHEL/Fedora etc.. download and install this: wget http://www.proxmox.com/cms_proxm........
  • Telus Begins Enforcing Bandwidth Caps


    Telus Begins Enforcing Bandwidth CapsIt appears Telus has begun to send e-mails out and is planning on enforcing bandwidth caps of only 10gigs/month for their 1.5mbit plan and 20gigs/month for 2.5mbit The state of Canadian ISPs is horrible :( In the east coast, Bell Sympatico will allow you to have unlimited bandwidth and even Aliant will and they have 3mbit for a much more affordable price than our 2.5mbit on Telus. Telus needs to get wit........
  • Clustered/Distributed Network Filesystems, Which Ones live up to the hype?


    I've tried to find a good sensible solution to cluster with and each technology has it's pros and cons and there is no perfect solution and I've found a lot of "exaggerations" in the applications, benefits and performance of these different filesystems. DRBD I first started off with DRBD and Ihave to say it does live up to the hype, is quite reliable (although it can be annoying to match up the kernel module and user applications since they must match and whe........
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