Re: Linux RAID & XFS Question - Multiple levels of concurrency = faster I/O on md/RAID 5?
From: John Robinson <hidden>
Date: 2008-11-01 12:14:44
Also in:
linux-xfs
On 01/11/2008 12:00, Justin Piszcz wrote:
On Sat, 1 Nov 2008, John Robinson wrote:quoted
On 01/11/2008 08:29, Justin Piszcz wrote: [...]quoted
Why is running 3 jobs con-currently that take care of two parts each more than twice as fast than running one job for six parts?Because you have multiple CPUs?So 1/4 of a quad core q6600 cannot achieve higher rates of I/O due to the parity operations being that costly? Is the only way to increase the single-threaded speed to increase the maximum CPU core speed/get a faster CPU, and/or theoretically a multi-threaded md-raid could maximize throughput?
Actually I was thinking that your test job - I think you said it used tar - is single-threaded and CPU-bound on one core, and doesn't saturate the MD subsystem. Your jobs are 75% user time to 25% system time, and the user time is not parellelisable until you do it yourself by splitting the work up. Cheers, John.