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philubonmat

SSD with Sata III slow speed issue

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Hello all,

 

I have an issue with Sata III, I get only 105MB/s write and 207.8 MB/s read

- SATA 6G PCI Express card

- Samsung SSD 850 EVO 250GB.  

- EL Capitan.

- Dell Precision 690

Screen_Shot_2017_07_23_at_4_24_48_PM.png

Screen_Shot_2017_07_23_at_4_26_04_PM.png

 

 

Any help will be appreciated

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Try with Trim disabled to compare, though little chance it'll change anything.

 

Since you're using a SATA III PCIe controller, its actual speed is limited by the PCIe's own lane speed. PCIe lane speed depends on the PCIe version (250MB/s for v1.0, 500MB/s for v2.0, etc.). You have to identify what version the Precision 690 uses. Then, know that different PCIe SATA controllers give different performance results.

 

See here for instance:

http://forum.osxlatitude.com/index.php?/topic/8701-marvell-88se91xx-88se92xx-based-pcie-sata-iii-controllers/

http://forum.osxlatitude.com/index.php?/topic/8732-syba-sd-pex50055-pcie-sata-iii-usb30-controller/

 

I've tested a few PCIe SATA-III controllers in my Precision 670 (the direct parent/ancestor of your Precision 690) and I experienced similar results as yours (just faster Write speeds): http://forum.osxlatitude.com/index.php?/topic/2061-dell-precision-470-670-workstation-snow-leopardlionmountain-lionmavericksyosemite/page-4&do=findComment&comment=56562

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Ok, Precision 690 is built around Intel 5000X chipset and that uses PCI Express v1.0. As such, your maximum theoretical speed per PCIe lane is 250MB/s. You would only marginally improve your experienced results with a different controller.

 

However, the integrated I/O controller of the chipset is SATA-II (300MB/s) so, assuming AHCI is available, you may find the SSD runs a little faster off that.

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Try with Trim disabled to compare, though little chance it'll change anything.

 

HI Hervé,

 

Disables and enabled the Trim got same speed. You are correct, the problem could be from PCIe bus. I tried to install Windows 10 on it and got same speed 

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