On 04/22/2013 06:48 AM, James Harper wrote:
My read speed is consistently around 40MB/second, and my write speed is
consistently around 22MB/second. I had expected better of read...
You may want to try increasing your read_ahead_kb on the OSD data disks
and see if that helps read speeds.
Default appears to be 128 and I was getting 40MB/second
Increasing to 256 takes me up to 48MB/second
Increasing to 512 takes me up to 53Mb/second
Any further increases don't do anything that I can measure
Is increasing read_ahead_kb good for general performance, or just for
impressing people with benchmarks? If the kernel spent time reading ahead woult
it hurt random read/write performance?
Potentially yes, but it depends on a lot of of factors. I suspect that
increasing it may be acceptable on modern drives, but you'll need to do
some testing to see how it goes in practice.
If anyone on the list knows how many sectors per track is typical for
modern 1-3TB drives I'm dying to know. That would help us guess at how
much data can be writen/read on average without imposing any head
movement. :)
Thanks
James
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