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[iMX6Q] Poor SATA Write Performance

Question asked by David Müller on Oct 9, 2015
Latest reply on Oct 14, 2015 by David Müller

Hello

 

I have an i.MX6Q based SabreSDB running Freescale kernel 3.14.28, alternatively a home-brew vanilla 4.1.0 kernel.

All four cores running at 996MHz, "cpufreq" set to "performance".

Using a SATA-to-CFast adapter and a SATA-II capable CFast card, I tested the SATA write perfomance of the i.MX6Q.

 

To simulate a "real-life" situation (with all the system overhead included), I created a shell script which copies the same file (10MiB in size) 20 times (using different target names) from a ramdisk to a 1GiB VFAT partition on the CFast card.

The time is stopped once the final "sync" returns ensuring all the internal buffers are flushed.

 

Above test sequence results in a SATA write speed of at most ~50MiB/s.

 

I also tried an Intel 330 Series SSD attached directly to the SATA port of the SabreSB port, but the result is more or less the same.

 

The same test done on Intel based systems (using vanilla 3.14.28 and 4.1.0 kernels) results in SATA write speeds of up to ~130MiB/s therefore it seems that the i.MX6 itself (hardware and/or software) is the limiting factor.

 

What "real-life" SATA write speed could I expect from a i.MX6Q based system?

Are there any bandwidth limitiation in the SATA area of the i.MX6, similiar to the limitation of the FEC?

Does anybody have some comparative values from similiar "real-life" applications?

Or is the ~50 MiB/s already the upper limit for an i.MX6Q based system?

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