34. Arquitetura Buffer Buffer DC1 DC2 DC3 Redundância de Data-Centers Escalabilidade Horizontal Alta Disponibilidade Plano B Escalabilidade Horizontal Sharding Redundância Replicação
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Notes de l'éditeur
Often attributed to Gates in 1981. Gates considered the IBM PC's 640kB program memory a significant breakthrough over 8-bit systems that were typically limited to 64kB, but he has denied making this remark. Also see the 1989 and 1993 rem arks above. I've said some stupid things and some wrong things, but not that. No one involved in computers would ever say that a certain amount of memory is enough for all time … I keep bumping into that silly quotation attributed to me that says 640K of memory is enough. There's never a citation; the quotation just floats like a rumor, repeated again and again.
Real Time - A real time system may be one where its application can be considered (within context) to be mission critical . The anti-lock brakes on a car are a simple example of a real-time computing system — the real-time constraint in this system is the time in which the brakes must be released to prevent the wheel from locking. Real-time computations can be said to have failed if they are not completed before their deadline, where their deadline is relative to an event. A real-time deadline must be met, regardless of system load . Hard and Soft - th e goal of a hard real-time system is to ensure that all deadlines are met, but for soft real-time systems the goal becomes meeting a certain subset of deadlines in order to optimize some application specific criteria.
CouchDB: B est used: For accumulating, occasionally changing data, on which pre-defined queries are to be run. Places where versioning is important. Redis: Best used: For rapidly changing data with a foreseeable database size (should fit mostly in memory). Mongo: Best used: If you need dynamic queries. If you prefer to define indexes, not map/reduce functions. If you need good performance on a big DB. If you wanted CouchDB, but your data changes too much, filling up disks. Cassandra: Best used: When you write more than you read (logging). If every component of the system must be in Java. ("No one gets fired for choosing Apache's stuff.")