Sutff about my job and comments about personal activities. Take a look to the first idea.

Monday, April 27, 2009

Wireless roaming with Wireless Access Points

For the record...

What is "roaming" and how does it work?
Roaming is the ability of a wireless computer user to communicate continuously while moving freely throughout an area greater than that covered by a single access point. In such a system, the users end node undertakes a search for the best possible access to the system. First, it evaluates such factors as signal strength and quality. Based on that information the node next selects the strongest Access Point and registers its address. Communications between end node and host computer can then be transmitted up and down the backbone. When a node no longer receives acknowledgment from its original access point, it undertakes a new search. Upon finding a new access point, it then reregisters, and the communication process continues.

Monday, November 17, 2008

Traffic sumulation

This is a nice traffic simulation.. so, try it just for fun
Microsimulation of road traffic

Sunday, August 10, 2008

Disk Recovery

Last month I found a hard disk damaged while trying to back it up with partimage, so I had to do some recovery using knoppix + ddrescue, I found a good step-by step know-how in cgsecurity which explained breifly how to do it... and finally I found a good story on hard disk recovery. Partimage is a really easy tool to backup... and even let me knew about hard disk errors... Cheers to Francois Dupoux and Franck Ladurelle creator of partimage and Antonio Diaz Diaz creator of ddrescue

The procedure booting with knoppix
Download latest version of ddrescue and compile it
$ wget http://download.savannah.gnu.org/releases/ddrescue/ddrescue-1.8.tar.bz2
$ tar xfj ddrescue-1.8.tar.bz2; configure; make
Turn off messages of console
$ dmesg -n3
Read good disk sectors
$ ./ddrescue -n /dev/old_disk /dev/new_disk rescued.log
Read damaged sectors
$ ./ddrescue -r 1 /dev/old_disk /dev/new_disk rescued.log

Wednesday, June 25, 2008

Wikipedia Infrastructure

Pretty nice that current infrastructure is: 200 application servers, 20 database servers and 70 servers dedicated to Squid cache servers... which squids servers are the ones that help maintain little cpu resources.

Besides, it uses Memcached and the Linux Virtual Server load balancer and also uses database sharding to set up master-slave relationships between databases.

Read more here

Wednesday, May 07, 2008

Google Reader notes

Finally, a cool option in google reader to add notes to share... read more at lifehacker