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Blockdev vs /sys/block/


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    #1  
Old 06-12-2014
Sergiu-IT's Unix or Linux Image
Sergiu-IT Sergiu-IT is offline
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Blockdev vs /sys/block/

Hello,

I want to set/get the read-ahead for my disks and there is a little issue that confuses me. There are three ways to get/set the read-ahead buffer:

1. cat /sys/block/md0/bdi/read_ahead_kb
2. cat /sys/block/md0/queue/read_ahead_kb
3. blockdev --getra /dev/md0

Which one is the correct one? The first two gives me a value of 128. The last one gives me a value of 256. Where does this difference come from?
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    #2  
Old 06-12-2014
vbe's Unix or Linux Image
vbe vbe is offline Forum Staff  
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Well I dont have much linux knowldge, but since you are talking disks, the same philosophy should apply:
First two give you a value of 128 (kb)
The last, blockdev since to talk like ioctl etc... and so is in blocks ( of 512 bytes) 256 block of 512 bytes...
To me then the values are much the same
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    #3  
Old 06-12-2014
Sergiu-IT's Unix or Linux Image
Sergiu-IT Sergiu-IT is offline
Registered User
 
Well... it makes sense, now

Thank you for your answer, vbe!
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