Slow Sd card write speeds

ernbrdn

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Nov 2, 2010
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I have installed Cyanogenmod 7 RC1 on my evo, but I experienced this as well on other roms I had installed. My write speed to my SD card over usb is around 1 meg a second, and this is on a class 10 card. my read speed is 17 megs a second which seems right but the write speed is way off. Is there a way to fix this? If I take the card out of my phone I get 11 MB transfer so it seems like it has to be a setting in the phone or maybe the kernel that I am using. Anyone else experience this?
 

cloak.n.dagger

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Jun 24, 2010
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Use file explorer and check your /sys/devices/virtual/bdi/179:0/read_ahead_kb file. Many ROMs use a Kernel that have this value set to 1 or 4. If you have root explorer (or a file explorer with root privledges) then you should be able to change this value ti 128 and save it. Others have reported huge SD card speed increases with this change, depending on the class of the card of course.
 

ernbrdn

Active member
Nov 2, 2010
28
1
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Visit site
Use file explorer and check your /sys/devices/virtual/bdi/179:0/read_ahead_kb file. Many ROMs use a Kernel that have this value set to 1 or 4. If you have root explorer (or a file explorer with root privledges) then you should be able to change this value ti 128 and save it. Others have reported huge SD card speed increases with this change, depending on the class of the card of course.

The read ahead was already set to 128, I downloaded an app called Sd Tools and it showed the read and write speed on the device as 10+ MB/s yet when plugged into usb is only transfers around 1 MB/s very frustrating
 

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