Can't understand this SSD spec

Question

Why is interface 6 Gb/s when the max sequential read is only 550 MB/s and max. random read is only 380 MB/s?

Even if this is doubled to include simultaneous read and write, that is way less than what the interface is capable of?

Does this mean that this interface is shared in case there are multiple disk? Then, does it mean that each physical machine can have only 1 such interface?

http://www.samsung.com/global/business/semiconductor/minisite/SSD/global/html/ssd850pro/specifications.html

score 6 · Accepted Answer · edited Mar 29 '16 at 16:44

6

It isn't actually that much less than the interface is capable of.

550 MB/s == 8 bits per byte * 550 MB/s == 4400 Mb/s == 4.4 Gb/s
380 MB/s == 8 bits per byte * 380 MB/s == 3040 Mb/s == 3.04 Gb/s

GB = GigaBytes Gb = GigaBits MB = MegaBytes Mb = MegaBits

See https://en.wikipedia.org/wiki/Data_rate_units for more details.

edited Mar 29 '16 at 16:44

Massimo

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answered Mar 29 '16 at 16:43

Jed Daniels

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score 3 · Answer 2 · answered Mar 29 '16 at 16:40

3

There is a difference of 8 between bits and Bytes.

The device is capable of saturating a SATA 2 connection. It is under the limit for a SATA 3.0 connection.

answered Mar 29 '16 at 16:40

84104

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score 0 · Answer 3 · answered Mar 29 '16 at 17:25

The 6 Gbps number is just telling you that it works with a SATA III bus, as opposed to just SATA I or SATA II bus.

You might have a drive where the raw flash can do 550 MB/s, but if it's only able to use a SATA II 3 Gbps bus then after you make the bit to byte conversion you'll find that the bus is actually limiting you, as 550 * 8 = 4400, which is greater than SATA II's 3000.

Can't understand this SSD spec

3 Answers3