Một trong những công nghệ mới mà bạn phải lựa chọn, nếu bạn dự định mua một máy tính mới hay một thiết bị ngoại vi, là USB (Universal Serial Bus) loại nào. Cho đến nay USB 2.0 đã là tiêu chuẩn cho nhiều năm qua, nó sẽ được thay thế bằng một phiên bản mới hơn 3,0. Mời các bạn khám phá sự khác biệt.
One of the new technologies that you might have to make a choice if you plan to buy a new computer or a new peripheral, this Fall is the USB (Universal Serial Bus) type. So far, the venerable USB 2.0 has been the computing peripheral de facto standard for years, it will be replaced with a newer 3.0 version.
Existing laptop users can upgrade to USB 3.0 capability with an adapter ExpressCard (e.g. Vantec 2-Port SuperSpeed USB 3.0 ExpressCard 34
“Most makers of hard-drives put it more simply: USB. 3.0 drives should be 10 times faster than USB. 2.0 models” , the common marketing message that you will see.
USB 3.0 official specs shows a theoretical maximum data transfer rate of 5 gigabits per second compared with a maximum rate of 480 megabits per second for USB 2.0 – On a side note, I would rather see the data speed for storage rated by “byte” and IP/LAN/WAN speed rated by “bit”, where a “byte = 8 bits” . The data transfer rates should read roughly 500 megabyte/ sec and 50 megabyte/ sec respectively or USB 3.0 promises 10x improvement in data transfer. Both initiator (e.g. your computer USB port) and target (e.g. disk drive) have to have the same USB 3.0 to yield maximum speed. They are, however can interoperate between versions at the lowest common denominator.
In real life, data transfer rate is just the speed from which a payload can move from point A to point B, which is very different from the response time that user sees. The total response time includes so many latency factors from key stroke, application initiates the I/O, sending blocks through the pipe, going to the disk controller cache and it might also include going to disk sector if the cache is full…..and the acknowledgment back to the OS and application.. for a write operation.
In a real-life test perform by the NY Times, the gain for a 10GB payload in write is 300% (6.5 minutes versus 22 minutes) and in read about 20% (4 minutes versus 5 minutes). The figures are far less than 10x or 1000% claimed by the marketing message.
As always, early adopters have to pay more for the bleeding edge experience. Unless you transfer very large files frequently – the additional costs might not justify.
