From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Fjellstrom Subject: Re: recommended way to add ssd cache to mdraid array Date: Sat, 12 Jan 2013 07:44:19 -0700 Message-ID: <201301120744.19386.thomas@fjellstrom.ca> References: <201212212357.19292.thomas@fjellstrom.ca> <201301111944.33921.thomas@fjellstrom.ca> <50F11FE2.8090701@hardwarefreak.com> Reply-To: thomas@fjellstrom.ca Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50F11FE2.8090701@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: stan@hardwarefreak.com Cc: Chris Murphy , linux-raid Raid List-Id: linux-raid.ids On Sat Jan 12, 2013, Stan Hoeppner wrote: > 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? Could have a tool like tune2fs, if you have to remount anyway, putting the non option option behind a tool would make it less dangerous for people who don't know they aren't actually changeable. > >> 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. I don't think theres a reason to be hostile. I had been meaning to join the XFS list, but usually, I get so far into looking into this stuff, before I run out of time and have to get back to work. As it is this new NAS box has been sitting on the floor doing nothing for a month or so waiting for me to have time to finish configuring it. -- Thomas Fjellstrom thomas@fjellstrom.ca