Επίσκεψη στο CoLab

Χτες μετά από τη δουλειά μαζί με τον @kotsgeor επισκεφτήκαμε το CoLab. Μας υποδέχτηκαν ο Σταύρος και ο Σπύρος. Μας ξενάγησαν στον (πολύ όμορφο και ζεστό) χώρο και μας μίλησαν για το τι σκέφτονται για το CoLab και τις συνέργειες που επιθυμούν να ξεπηδήσουν μέσα από αυτό. Τα παιδιά είναι ανοιχτά σε ιδέες από τους επισκέπτες ώστε να μπορούν να προσφέρουν μέσα από το χώρο ότι περισσότερο μπορούν για τους υποψήφιους χρήστες του. Δεν αρνήθηκαν να απαντήσουν σε καμία μας ερώτηση, όπως π.χ. τιμολόγηση των παρεχόμενων υπηρεσιών (που δεν υπάρχει ακόμα στο site).

Flashback: Από το 1990 μέχρι και σήμερα έχω δει πολλούς χώρους που θα τους ονομάζε κανείς hackerspace. Έχω δει ιδέες καλές, κακές ακόμα και καταδικασμένες να κάνουν τον κύκλο τους. Έχω δει να οικοδομούνται σχέσεις φιλίας, εμπιστοσύνης και σεβασμού στην ικανότητα, όπως έχω δει επίσης να συμβαίνει ένα απίστευτο μοίρασμα της παραγόμενης γνώσης. Ήμουν εκεί όταν κάποιος είχε μια πραγματικά εφυή ιδέα και ξέρω αυτή τη λάμψη στο μάτι. Έχω δει το αποτέλεσμα. Σε όλα τα παραπάνω όμως δεν υπήρχε κάτι, στο οποίο στοχεύει το CoLab. Το οικονομικό κίνητρο των χρηστών του χώρου. Γιατί οι χώροι αυτοί ήταν πανεπιστημιακά εργαστήρια.

Εύχομαι στο CoLab καλή αρχή και να εκπληρώσει το σκοπό για τον οποίο δημιουργήθηκε. Ερμού 44 στον πέμπτο όροφο. Αξίζει να το επισκεφτείτε, να δείτε το χώρο και να μιλήσετε με τα παιδιά μόνοι σας.

Dear consultant

Dear (billable by the hour) consultant-

You are brought in to help us find a solution. You are not to bring the one solution that you know and try to fit us in there. You are to find a solution that fits the client, not a client that fits the solution. So next time please present at least two different solutions (see here why), otherwise we are going to bill you for our time instead.

[ Inspired by discussions with colleagues from both the private and public sector ]

The other side

Δεν έχω συχνά την τύχη να βρίσκομαι μαζί με αρκετό κόσμο που δουλεύει με τον Exchange. Όταν όμως συμβαίνει αυτό, πάντα φεύγω έχοντας μάθει κάτι παραπάνω, όπως π.χ. την ύπαρξη των παρακάτω “ποστμαστερικών” blog που αφορούν κυρίως το συγκεκριμένο εργαλείο:

Please do not mix CNAME and MX RRs

From time to time I observe the following email setups, from web hosting providers mostly:

$ host -t mx example.com
example.com mail is handled by 5 mail.example.com.

$ host mail.example.com
mail.example.com is an alias for www.example.com.
www.example.com has address 192.0.2.2

In other words this is a single server that provides web and mail services, The devil is in the details though: mail.example.com is an alias for http://www.example.com. This is a mistake as when something is declared as a CNAME, it cannot have other resource records bound with it. I copy from DNS for Rocket Scientists:

CNAME RRs cannot have any other RRs with the same name, for example, a TXT – well that was true until DNSSEC came along and in this case RRSIG, NSEC and certain KEY RRs can now occupy the same name.

So the above setup is wrong. The correct setup would be the following:

$ host -t mx example.com
example.com mail is handled by 5 mail.example.com.

$ host mail.example.com
mail.example.com has address 192.0.2.2

$ host www.example.com
www.example.com is an alias for mail.example.com.
mail.example.com has address 192.0.2.2

That is if you want to use a CNAME at all. Personally I am using A RRs instead of CNAMEs whenever possible. But why cannot a CNAME carry any other information? I copy from RFC1034 (section 3.6.2):

A CNAME RR identifies its owner name as an alias, and specifies the corresponding canonical name in the RDATA section of the RR. If a CNAME RR is present at a node, no other data should be present; this ensures that the data for a canonical name and its aliases cannot be different. This rule also insures that a cached CNAME can be used without checking with an authoritative server for other RR types.

So please people, correct your defaults. Your clients will benefit from that.

How Metcalfe’s Law explains the attitude of your sysadmin (or what you perceive as negative behavior)

A poster over at ServerFault complained about the attitude some sysadmins show towards their users, even when the task seems simple and can take as little as 30 minutes maximum. Many users share similar concerns / complaints:

“Every time I ask a simple request like [simple request], these guys act like i’m asking them to build the great wall of china overnight. I’ve had to do this myself many times, it takes under 30 minutes, and maybe 30 seconds of user interaction.”

Or so the poster thinks. There are enough answers that show why comparing stuff you do on a single system are not to be compared with stuff you do when inserting a new system into an already working web of systems with provisioning and established procedures in place. But even when it is only a matter of 30 minutes, it is also a matter of when these thirty minutes will be devoted. Users do not know about RMS or EDF and do not understand that in an interrupt driven line of work sysadmins use intuitive variants of them. I want to expand however on a comment I posted there which links Metcalfe’s Law to the problem. Metcalfe himself has written about the law:

“[Nobody] has attempted to estimate what I hereby call A, network value’s constant of proportionality in my law, V=A*N^2. Nor has anyone tried to fit any resulting curve to actual network sizes and values.”

For simplicity most refer to the law by using V ~ N^2. Note though that in the same blog post Metcalfe points that the constant A (which we conveniently omit most of the times) may change while N increases and may even be a more complicated function of N. He urges people to look into that.

Metcalfe's original slide presenting the Law, circa 1980

What Metcalfe defines as value, is what we, system administrators, lift for a living. So when a service is down and your sysadmins work like crazy to bring it back rest assured that they already know what is at stake. Metcalfe made sure of that. And that is why it does not really help asking them every ten minutes “When is it going to be up again? We are losing money!” Not only do we know, we do not even need a napkin for our guestimate.

And that is why what for the user is “just another server” or “just one more service” and therefore going from N to N+1, actually means that the load to be lifted increases by 2N+1. No it is not just another server or service for it is not independent. It is inserted in an already complex system and it must be done so in a way that does not affect the stability of the (new) whole. Rolling back, if things fail, is a myth. This is a lot more complicated than your testbed setup which no matter how complex, is simple enough. Consultants and other “out of town experts” routinely make this mistake.

A schematic may make it easier to understand. We all know the corporate pyramid, where “the top” is the target (or the result of the Peter Principle in action) of workers within an organization. But within organizations, a second (inverse) pyramid forms, a pyramid that explains your sysadmin’s day:

A day in the life of your sysadmin

It’s no wonder that, even putting personality and character deficiencies aside, your sysadmin looks grumpy at times. Like the Last Electrical Engineer, his work is of infinite weight and importance, but invisible to the known (organizational) universe.

Remember, pressure brings tension.

$5/year and the Paradox of Choice

It has been over a month since I purchased 20G of disk space from Google for $5 per year. Given that a relatively cheap 32G USB drive is being sold for €19 this is a bargain (including the risk of not being able to access my stuff over the network).

The reason I bought space from Google, was because I wanted to upload “My Documents” (PDF mostly) to a single place where I could access it from any computer I work from and always be in sync. By the way, for non-documents I am using MyNetworkFolders.

But here is where the Paradox of Choice emerges: In my “Books” directory I see over 200 ebooks (Math and CS-Math related mostly). They are either O’Reilly titles (including a few from Apress less than 20) or interesting books that have been made available online. Picking them up and filing them in a directory is quick and easy (Hey a book on Optimization, another on Topology, etc let’s keep a copy around). Can you imagine the actual space that 200+ hundred books would occupy? Would the bookshelf cost $5 per year? But then again how many of these books will I ever manage to read in my lifetime? At least it seems that sometimes when someone has a question, the answer may have already been downloaded.

The speed and easiness of the delivery are making us somewhat less picky (or alter the way we research before grabbing a book). I was having a similar discussion with a friend who is a professional photographer and he observes that people click far too many (digital) photographs which they file away and forget, as opposed to taking the time and shooting less photographs (because film was expensive, developing took time, etc) which they enjoyed viewing more. As Ashby said only variety can destroy variety.

Prolog books found online

This is an incomplete list of books about Prolog that can be found online:

I am counting on readers’ comments to grow it.

Update by ΤΖΩΤΖΙΟΥ:

άνευ τίτλου

* Κολυμβητήριο ΟΑΚΑ, 2010/10/20 *

– Μα αν αφήσετε τα πράγματά σας στα αποδυτήρια, πως θα μπορέσω εγώ να ντυθώ;
– Α, αυτό δεν είναι δικό μου θέμα.
– Μα αυτό που κάνετε δεν επιτρέπεται!
– Και ποιος το λέει αυτό;
– Η ταμπέλα

ΟΑΚΑ, 2010/10/20

– Α να σας πω! Δε με ξέρατε και από χτες για να μου μιλάτε έτσι!
– ?!?!

Και επειδή η γαϊδουριά πάει σύννεφο, τα πράγματα τα άφησε εκεί.