Monday, December 30, 2013

Data integrity and the Time Machine Restore

Information Technology is all about data. We collect raw data to build inferences on them and then store results keeping logs. We make decisions on strategical policies using data trends. We bill our customers on their service consumption data. Our bank adds and subtracts cash amount data (not bucks), etc. 
The 19th century was the century of steam, the 20th the century of transistors, this one is the century of data. The data give the power to manage trends, anticipate and influence consumers behavior, the control financial transactions and a lot of other stuff that all great companies well know.  
Please, do not to be fooled by your last generation smart phone, your tablet or your android stick. They will be obsolete in few months. Well collected and elaborated data are like gold. You can buy data or to mine them, it doesn't really matter, but you have to keep them in a safe place.

Friday, December 27, 2013

The Osi Stack. the number Seven. the Parsley and Katy Perry

The Osi stack model is like parsley  in Italian cooking (for my fellow non Italian SAs: I have to say you something. Please, have a seat and try to control your reactions. We Italians do not use parsley everywhere like you think we do. I.e. we do not use it in Bolognese sauce or as pizza's toppings. Parsley is allowed in Marinara sauce and, generally, in combination with garlic -not too much if you want to kiss someone instead of having dessert - but parsley is absolutely forbidden everywhere onions are used and you have to add it at the end to avoid parsley to be overcooked. Now, you know the truth and you have the power. Use it with responsibility).

Tuesday, December 24, 2013

Networks: Circuit Switching Vs. Packets Switching

A network is set of artifacts (or simply procedures) that allows network terminals to share information each other. So, a tin can phone can be considered a kind of network without doubts.
In the Hyperuranium network model ( usually Hyperuranium citizens are software people and CEOs ), a network is a complete graph. It means that every network end is connect to all other ends. Please, have a look at following picture:

Please continue reading this post on my new wordpress site.

Monday, December 23, 2013

Bandwidth, Round Trip Trime (RTT) and Latency

In a world wide distributed computing environment, the large scale in terms of users and transactions spread over the whole planet becomes the main factor for performances.
Cheap hardware availability, strengthening of CPUs and growing sizes of RAM seem still have margins of growth, on another hand, network and disk spindles (we'll talk about spindles in a future post)  are the worst nightmare for SAs.
You can scale web server front ends, create master and slave databases or federated them with the best hardware layer 7 load balancer, to cache data in a well organized LRU cache farm, but you can't do too much on physical limitations of mechanics and electromagnetism.

Sunday, December 22, 2013

The Underestimated Power of Copy and Paste

Someone, including me, thinks that one of the greater computer science inventions is the "Copy & Paste" stuff. Late in the 80's, when I started programming in Pascal and AIM65 assembler language, I had to use VT100 and VT340 terminals. Yes, "vt100" isn't only a value for the environment variable TERM. It is (it was) a physical terminal connected to a kind of serial hub called terminal server. I have evidences. One follows

Tuesday, December 17, 2013

A New Scale

Please, have a look to the interesting presentation that +Todd Underwood  showed in past November at Washington Usenix Meeting. Here you can find the audio, PDF and video version. Try the video, it worth to be seen.

Old good fella like me are always curious about how young guys are keeping on the golden SA's tradition, but, please, don't say to Todd that I called him "system administrator".

Sunday, December 15, 2013

Good ol' times

There was a time when a refrigerator sized machine with 500 MB disk space and 64 MB of ram memory powered with 380 V, cooled with water pipes and a small cubicle for the "embedded", system administrator wearing a white coat,was called "mini computer".
It isn't a joke. The "mini" was only the silly cousin of the big one, the apartment sized mainframe connected to a tape jukebox large like the the brick pig's house.

Past is like Texas. Everything looks big. I thought about it when I was silently complaining for the bad graphic interface of a chess game on my 900 grams, 10", 64 GB tablet. My first programming experience was on an AIM 65 where I wrote my own 30 instructions assembler version of eight queens puzzle using 6502 machine language.
It was in the late 80s, when I was still a fireman. Until now, it had been a story of algorithms, protocols, Internet, network services, security, smiles to frightened software people and screwdrivers, a lot of screwdrivers. 

May be, someday, I'll find time to tell it.

Coming soon

I'll be back in the next few days with a real post, not only a placeholder. If I don't, you are authorized to define these "my last famous words".