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SATA, Gain or Pain?

By hanekwj ·
I have several SATA 3.0GT/s HDD in my PC. manufacturers say that SATA 3.0GT/s should deliver up to 300MB/s but testing my SATA drives by copying a 5GB .iso between them i only get 55MB/s. When I transfer a 1GB .iso the transfer speed is 70MB/s so it seems the smaler the file the faster the transfer? between a SATA and a PATA drive i transfer 27GB at 33MB/s

This is all according to Windows Vista's calculations.

All drives has caching enabled.

Are these speeds normal?
Are these speeds acceptable?
Is Windows Vista Accurate?
Can i do anything to improve transfer speeds?

the drives are NOT in Raid and all operate independantly

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Your terminology is all mixed up ...

by OldER Mycroft In reply to SATA, Gain or Pain?

For a start your HDDs are NOT 'GT/s'. they are 'Gb/s' - GIGABITS per second.

Your cited transfer rates of '70MB/s' is for MEGABYTES per second. There are EIGHT bits in a byte. Thus the transfer rate is 560Mb/s. - MEGABITS per second.

The rated speed for SATA is 300MB/s [which equates to 2.4Gb/s data throughput] and today's mechanical hard disk drives can transfer data at up to 127 MB/s so you are doing rather better than you think you are.

You'll have to pay closer attention to the differences between 'B' and 'b'. :)

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Two more things.

by Kingbackwards In reply to SATA, Gain or Pain?

First, when transferring between two devices, you will max you speed at the SLOWER device, because the transfer will only go as fast as the slowest device.

Secondly, when less data is sent the faster it will appear to go. Because the information the OS generates are just time and speed estimations based on how much data or how many files being transfers. Less data equals rougher estimates.

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One more thing

by TheChas In reply to SATA, Gain or Pain?

One more thing to take into account is that the rated transfer speeds are measured in a lab with direct transfer between a hard drive and a data buffer. Fully ideal optimized conditions. But, nowhere near "real world".

When you transfer data between 2 hard drives on a computer at least some part of the data path is shared. Thus, once your file size exceeds the of the smallest data buffer in the path, the transfer rate drops and will eventually be the slower of about 1/2 the data rate of the fastest device in the data path, or the data rate of the slowest device.

The worst case for data transfer between 2 similar devices is when they are both connected to the same drive controller on the motherboard. That is part of why it was best practice for PATA IDE systems to have the hard drive on 1 IDE cable and the optical drives on another.

Chas

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