• Home
  • Work
  • Blog
  • Security
  • Links
  • Samsung SSD 840: Endurance Destruct Test

    2013 - 10.10

    When you operate a Datacenter with many servers you also probably have big number of installed disks. In most cases even you have cluster, especialy in small companies, there is still SPOF (Single point of failure) somewhere.

    In this SPOF it’s critical to know condition of the system. When system using HDD it’s important to know HDD condition to prevent failures, plan maintenance etc.

    We will talk about Samsung SSD 840 PRO series. We realize this SSD has very good performance and lifetime. Before we use it in production we must know how to monitor condition. There is many articles and technical specification but we had a lot of questions without answer.

    ssd-disks

    (Update: 10.10.2013)

    (Samsung performance issues, read new post, 03.12.2014)

    Read the rest of this entry »

    Forgotten Skills: Build your own linux kernel

    2013 - 09.23

    Firt we will talk about WHY. Many people have many opinions on that and I’d like to present you mine.

    I work as System Specialist. During my work I often came to point that normal kernel from distribution doesn’t work. Whole or part of server was unusable because one of these common reasons:

    • Virtualization support with combination of new HW
    • Missing driver for some Raid Controllers
    • Missing driver for network cards
    • Security hardening patches for specific systems

    I don’t remember which of the reason was the first when I must build my own kernel to be able use server or computer with all it’s hardware. In few next years another big reason appear.

    • New kernel have fixed some performance issues

    Now we can talk about how to do it.

    Read the rest of this entry »

    HowTo use Grub rescue mode

    2013 - 06.07

    Sometimes when you upgrade or migrate your linux from one disk to another, boot should hang out on line  “grub rescue>“,

    what now ?

    Read the rest of this entry »

    Configure different DNS resolvers for domains in Ubuntu

    2013 - 06.04

    This is simple How-To which describe how to configure Ubuntu to use different DNS servers for various domains. It’s very useful feature when you want to connect to your office VPN and use office DNS servers for intranet domain but for other domains you want to use your own or your ISP DNS servers.ubuntu-logo

    Situation:

    • domain.intra – resolve hosts from dns server 192.168.30.1
    • home.intra – resolve hosts from this domain from 192.168.0.1
    • other domains resolve from your default DNS server (ISP, or home etc.)

    Read the rest of this entry »

    BASH GIT prompt

    2012 - 11.28

    I’d like to introduce you my bash shell which can handle GIT information.

    More information and sources are hosted on Github.

     Basic prompt

    Read the rest of this entry »

    Protect your announced IP prefix on the Internet

    2012 - 11.03

    Many companies which provide various type of services which are depends on the internet have their own IP prefixes. They announces prefixes to the internet using BGP protocol and AS numbers.

    From the principle of BGP, it’s possible to break path to your servers if somebody announce same prefix as you. This is really big problem because your business is in risk. Communication is problematic and takes lot of time. Normaly, providers and peers should have configured some rules, filters and other types of security to prevent this.

    Using filters isn’t mandatory, so it can happen and it happened many times.

    Question is, what you should do to avoid this situation ?

    Read the rest of this entry »

    Automatic server audit for RackTables project

    2012 - 11.02

    First I’d like to introduce one very nice project called RackTables. It’s management system for DataCenters or rack rooms. I test many project like this but this one fits best for our needs. With this system you can document your network and infrastructure. Datacenters, rooms, rack rows, servers and their attributes, ipv4/ipv6 ranges, virtual resources, etc.

    I work as System Specialist, many times it’s too much work and I forgot to document some changes which I made on server or infrastructure. When number of servers grows to hundreds this is a really big problem you must handle. Important is also to know, what was the change, not only actual state. So you must create log of changes.

    I have created one small script which discover physical or virtual server and insert or update information into racktables database and ! it create LOG in RackTables. You see what was the previous state and when this change was made.

    Script can handle various system and HW infromation and what is perfect, it do it automatically without any interaction.

    Read the rest of this entry »

    IBM server x336 modification SCSI to SATA – 2 (LED Indicators)

    2012 - 05.17

    This is small update of article about modification server IBM x336 from SCSI to SATA.

    Today I’d like to talk about front LED indicators.

    Our cheap sata backplane has two outputs for LED indicators. One is for power and one for activity.

     

    I’ve bought two colors led for indication power and activity of each HDD. As I dicovered later activity output not work properly.

    Read the rest of this entry »

    Enable google talk to work with your own domain

    2012 - 05.15

    It may look easy but it’s very hard to find the correct setting.

    On google help site is not complete setting if you want to make your domain fully working with google talk.

    I was searching but it’s also very hard to find.

    I’d like to specify what I mean if I say “Fully working”.

    1. Chat outside google domain (you could find settings on google site)
    2. Connect from all clients

    Read the rest of this entry »

    IBM server x336 modification SCSI to SATA

    2012 - 05.09

    Few months ago I bought some older IBM servers. Two cheap iBM x336 with 4 GB RAM and two SCSI disks.

    After first look I decided to use ona server as my new server with two 146 GB SCSI disks and FreeBSD installed and second server modify for two SATA disks. SCSI disks are great but more expensive and lower capacity then SATA disks.

    I’d like to explain how to modify IBM X336 SCSI version and using it with SATA disks. During modification there was many obstacles that I need to solve.

    Read the rest of this entry »