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From Doug Cutting <>
Subject Re: detected corrupted index / performance improvement
Date Fri, 08 Feb 2008 19:28:45 GMT
Doug Cutting wrote:
> The linux 
> kernel dynamically increases the readahead window based on the access 
> pattern: the more you read sequentially, the larger the readahead window.

Sorry, it appears that's in 2.6.23, which isn't yet broadly used.

In the meantime, on Linux, one can set both the kernel's readahead 
buffer size and the device's.  These are additive: the first determines 
what requests will be made to the device, the second determines how much 
beyond that the device will attempt to read.

# set kernel read-ahead buffer to 1MB
echo 1024 > /sys/block/sda/queue/read_ahead_kb

# set device read-ahead buffer to 1024 sectors
hdparm -a1024 /dev/sda1

I don't know how much these actually help things...


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