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VM role - o noua dimensiune pentru Windows Azure

Windows Azure permite pana in acest moment doua tipuri de instance:
  • web role - similar cu 'Web Application', in principiu orice ce merge pe http si https;
  • worker role - similar cu un 'Windows Service', ruleaza neincetat prelucrand date;
Nu vreau sa intru in amanunte pe aceasta tema. Pe langa aceste doua, Microsoft ne pregateste un nou rol, denumit VM role. In momentul de fata este in ultima faza de testare, urmand sa apara pe piata cat de curand.
VM role-ul o sa ne permita sa controlam in intregime masina. Este nevoie sa cream local local un VM role pe care apoi sa il copiem in cloud. Pe el o sa putem pune de exemplu Windows Server 2003, putem sa controlam tot ce este instalat pe el. Singurul dezavantaj este partea de administrate care o sa fie facuta in totalitate de utilizator. O parte din pachete de update de exemplu nu o sa mai fie facute automat sau configurarea nivelului de securitate. Iar cloud-ul NU ne ofera back-up la aceasta instanta in mod automat. In cazul in care instanta moare, imaginea care o sa fie folosita este cea pe care am trimis-o ultima data spre cloud. Imaginea care este pusa pe cloud si care este folosita de catre instance pentru a initializa un VM role se numeste "golden image".
Putem sa controlam totul pe aceste intante, de la sistemul de operare la ce aplicatii ruleaza si in ce fel. Dar acest lucru se poate intoarce impotriva noastra, trebuie sa facem si partea de administrare, care poate sa fie uneori costisitoare, nu doar din punct de vedere a timpului cat si financiara.
Se recomanda folosirea acestor tipuri de instante in cazul in care configurarea unui web/worker role ia mai mult de 5 minute. Aici nu stiu ce sa zic, s-ar putea ca noi sa nu fi gandit corespunzator modul in care noi facem deploy.
Chiar daca VM role poate sa para pentru unii un vis devenit realitate, eu il vad mai mult ca in compromis. Trebuie din nou sa facem partea de administrare, licentiere si alte lucruri care cresc pretul final si complexitatea proiectului. Trebuie sa avem un motiv intemeiat cand dorim sa alegem aceasta optiune( poate se preteaza pentru aplicatiile deja scrise, in cazul carora costul portarii pe cloud ar fi destul de mic).

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