Doug Rau
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Homepage: http://www.iphouse.com/
Posts by Doug Rau
SysAdmin Golf: The Hard Way
Dec 9th
This is the hard way to p2v a Linux server into a vmForge VDC. You’ll need the VMware Converter bootable CD, and somewhere to store your disk image. If you have a Windows server and shared disk on your local network, that may be faster than a USB hard drive, which is what I used. This is a cold clone procedure, which means that your server is down while its being copied. And it may be down for a while, depending on how much disk your server has, how quickly it can be cloned to local storage, and finally how quickly it can be uploaded to your VDC.
uncomplicated firewall
Dec 2nd
ufw, or uncomplicated firewall, is the default host firewall tool for Ubuntu and is designed to be easy to use.
unless you don’t realize that its been enabled for you, in which case you’re likely to spend an hour bashing your head into something trying to get nfs to work. ufw is normally driven from the command line, although a GUI is also available.
you’ll need to have root privileges to run ufw.
comparing software load balancers
Dec 1st
now that i have three different software load balancers installed (Balance, Crossroads, and Pen), i want to evaluate their relative performance. benchmarking a single web server isn’t difficult using tools like ab, but trying to benchmark a load balanced cluster is somewhat different. since most load balancers support stickiness, all the requests from a single source will be directed to a single back-end server. thus, i’ll need to run the benchmarker from several different sources simultaneously, or i’m really just testing one server with something in the way. fortunately, i have three machines on different IP addresses sitting idle.
software load balancing
Nov 29th
load balancing is a common technique for distributing a workload, such as handling a web site, across multiple servers. a pool of several smaller servers can be more efficient than a single large server, since the size and capability of the “server” can be changed just by adding or eliminating servers from the pool. a pool of servers can also be more responsive than a single server, and more fault-tolerant.
one of the simplest forms of load balancing is round-robin DNS, where a single hostname is pointed at multiple IP addresses, each of an individual server. this is very easy to set up, but changes to the pool are limited by DNS caching and TTL. on the other end of the spectrum are dedicated hardware load balancers, such as the F5 Big-IP we use, which monitor the status of each server in the pool and intelligently route incoming requests. these are awesome machines, but come with equally awesome price tags. between these two extremes lie some network firewalls with load balancing, and software load balancers, which run on a front-end server.
i’ve been looking at a few software load balancers for a small virtual server project; Balance, Crossroads, and Pen.
Reengineering in a Virtualized System
Feb 10th
In addition to scalability and redundancy, one of the advantages of a virtualized system can be a single point of configuration across multiple servers. This not only streamlines day-to-day maintenance, it can also facilitate making significant system engineering changes.
For example, several months ago, we looked to FastCGI to improve the performance of PHP scripts on our webhosting cluster. These scripts have always run under individual account UIDs for security, via mod_cgi and suexec. However, this additional overhead meant that PHP scripts took longer to run and required more CPU relative to the in-process execution of mod_php.
