SATA Bandwidth

[JezEngland]

Motherboards have SATA 3Gb/s and SATA 6Gb/s. Recently i got a SSD, my board has only SATA 3Gb/s. I looked at a Crucial SSD, its read speed is 355MB/s. That speed will work only on a SATA 6Gb/s. My knowledge of the maths involved is empty because 355MB/s is less than 3Gb/s and I don't know why the SATA 3Gb/s doesn't run the reading at this SSD's max speed. Can a SATA 3Gb/s read at 3Gb/s? Whats the formula involved?

The customer server at Crucial on the phone didn't know, he said "good question".

I requested a data sheet of the Crucial SSD and below is info about it for SATA 3Gb/s and SATA 6Gb/s

Crucial RealSSD C300 2.5"

SATA 6Gb/s Sequential R/W speed - 256GB - 355MB/s Read, 215MB/s Write 128GB - 355MB/s Read, 140MB/s Write 64GB - 355MB/s Read, 75MB/s Write Random 4k R/W - 256GB - 60,000 IOPS Read, 45,000 IOPS Write 128GB - 60,000 IOPS Read, 30,000 IOPS Write 64GB - 60,000 IOPS Read, 15,000 IOPS Write Read/Write Latency (typical) - 55us / 60us

SATA 3GB/s Sequential R/W speed - 256GB - 265MB/s Read, 215MB/s Write 128GB - 265MB/s Read, 140MB/s Write 64GB - 265MB/s Read, 75MB/s Write Random 4k R/W - 256GB - 50,000 IOPS Read, 45,000 IOPS Write 128GB - 50,000 IOPS Read, 30,000 IOPS Write 64GB - 60,000 IOPS Read, 15,000 IOPS Write Read/Write Latency (typical) - 70us / 95us

Thanks

 

[Toxteth O'Grady]

8 bits in a Byte.

 

[JezEngland]

ok, hmm, though 355 x 8 = 2840 wich is less than 3Gb

1 gigabit = 10 to the power of 9 bits = 1000000000bits.

1 gigabyte is 1000000000bytes

This is from Wiki: There are several units of information which are defined as multiples of bits, such as byte (8 bits), kilobit (either 1000 or 210 = 1024 bits), megabyte (either 8000000 or 8×220 = 8388608bits), etc.

I've known a Mega to be a million, so 1 Mega is 1,000,000, ahh so 1 Megabyte is 8,000,000 bits defined is 8388608 bits, OK

My maths sketch led to this equation: 355 x 8388608 = 2977955840. That is a little less than 3Gbit

Then I compared it to the SSD's SATA3Gb/s restricted speed: 265 x 8388608 = 2222981120. That is a little more than 2Gbit

This is from Wiki: Solid-State Drives have already saturated the SATA 3 Gbit/s limit at 285 MB/s net read speed and 250 MB/s net write speed with the Sandforce 1200 and 1500 controller

This is from Wiki: Giga is a unit prefix in the metric system indicating multiplication of a unit by 109 or 1000000000. It has the symbol G.

There's gota be some bandwidth usage elsewhere, like searching for the info on the drive though I think that'd not be using much bandwidth and probably wouldn't be in use when the search/communication has been executed

 

[S_I_N]

I think what you might be missing in ur equation is that 3Gb/s is what its CAPABLE of handling not what you'll get by hooking something up to it. Now if you had a SDD/HDD that did 3GB/s then you'd see it. Just cause a controller is CAPABLE of handling a certain speed does not mean that's what you'll get.

lol should of read your whole reply before posting that above

sorry I missed your point but what I said still holds true. please post once ya find the missing part of the equation