From: Jan Kara Subject: Re: which IO-scheduler is best for flash based storage device with ext4 Date: Wed, 13 Jan 2016 10:06:08 +0100 Message-ID: <20160113090608.GB14630@quack.suse.cz> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , "linux-ext4@vger.kernel.org" To: "HUANG Weller (CM/ESW12-CN)" Return-path: Received: from mx2.suse.de ([195.135.220.15]:36387 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750830AbcAMJGC (ORCPT ); Wed, 13 Jan 2016 04:06:02 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi, On Wed 13-01-16 06:33:28, HUANG Weller (CM/ESW12-CN) wrote: > Could you tell me which IO-scheduler is best for flash based storage > device with ext4 ? Just search from WWW, I saw it is said that the noop > is best because the CFQ is design for the mechanical hard disk. And I > did the performance test with IOzone between the IO-scheduler noop and > cfq. The performance difference is small. So here I want to get some > answer from you about this question. Yes, CFQ is meant for classical rotational disk. For normal SSDs I use deadline IO scheduler (it does more request merging, prefers read over writes), for high-end I'd use noop. Honza -- Jan Kara SUSE Labs, CR