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 02:33:38 -0600 Message-ID: <50F11FE2.8090701@hardwarefreak.com> References: <201212212357.19292.thomas@fjellstrom.ca> <201301111151.44384.thomas@fjellstrom.ca> <50F08F96.1050909@hardwarefreak.com> <201301111944.33921.thomas@fjellstrom.ca> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201301111944.33921.thomas@fjellstrom.ca> Sender: linux-raid-owner@vger.kernel.org To: thomas@fjellstrom.ca Cc: Chris Murphy , linux-raid Raid List-Id: linux-raid.ids On 1/11/2013 8:44 PM, Thomas Fjellstrom wrote: > On Fri Jan 11, 2013, Stan Hoeppner wrote: >> On 1/11/2013 12:51 PM, Thomas Fjellstrom wrote: >>>> It's not but as Stan writes it may not be preferred for your >>>> application. >>> >>> Hm, ok, it is in my mount line, so I'll try it with that off. Though I >>> would be interested in hearing from Stan why it may not be good. >> >> You should not do this. This parameter is not a toggle switch intended >> to be flipped on/off at will, but changed only once and left there. > > Makes me wonder why they are mount options if they aren't meant to ever be > changed? I'll answer that question with a question: If you were to implement a new (secondary) allocator on a 10 year old filesystem, by what mechanism would you have the user enable it? You can't change the allocator while the filesystem is mounted, so you can't do this with a sysctl. So if you must remount the filesystem to enable the new allocator, where do you enable it? Make sense yet? >> Never change XFS parameters willy-nilly without knowing the >> consequences. And currently you certainly do not know them. >> >> I don't have time for the detailed explanation. Ask on the XFS list. > > Alright, thanks for your help :) And as the last few times over many months, you never post to the XFS list. Which tells me you really don't care to learn this stuff. -- Stan