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From Bryan Talbot <>
Subject Re: tuning concurrent_reads param
Date Fri, 07 Nov 2014 00:33:49 GMT
On Wed, Nov 5, 2014 at 11:00 PM, Jimmy Lin <> wrote:

> Sorry I have late follow up question ....
> In the Cassandra.yaml file the concurrent_read section has the following
> comment:
> What does it mean by " the operations to enqueue low enough in the stack
> that the OS and drives can reorder them." ? how does it help making the
> system healthy?

The operating system, disk controllers, and disks themselves can merge and
reorder requests to optimize performance.

Here's a relevant page with some details if you're interested in more

> What really happen if we increase it to a too high value? (maybe affecting
> other read or write operation as it eat up all disk IO resource?)



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