From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: recommended way to add ssd cache to mdraid array Date: Sat, 12 Jan 2013 08:14:04 -0600 Message-ID: <50F16FAC.7000509@hardwarefreak.com> References: <2258826.8.1357992379424.JavaMail.root@zimbra> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <2258826.8.1357992379424.JavaMail.root@zimbra> Sender: linux-raid-owner@vger.kernel.org To: Roy Sigurd Karlsbakk Cc: Chris Murphy , linux-raid Raid List-Id: linux-raid.ids On 1/12/2013 6:06 AM, Roy Sigurd Karlsbakk wrote: >> Unlikely to make up the difference is the scheduler. Parallel fs's >> like XFS don't perform nearly as well with CFQ, so you should have a >> kernel parameter elevator=3Dnoop. >=20 > uh=85 how can the filesystem chosen be relevant to the disk elevator?= =20 It's the other way round. The chosen elevator can cause problems with the filesystem. You should find this relevant conversation amongst the lead XFS developers educational: http://oss.sgi.com/archives/xfs/2011-07/msg00464.html > CFQ will try to optimize access to reduce seeks "Completely Fair Queuing" -- The name alone tells you how it works. It most certainly does not do what you state. Please read the brief Wikipedia article: http://en.wikipedia.org/wiki/CFQ > and should be completely independent on the filesystem used on top. Operative word: "should" The USA should not be $16 Trillion in debt, but it is. By internationa= l law whales should not be killed, but they still are. Etc. --=20 Stan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html