From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wols Lists Subject: Re: [BUG] non-metadata arrays cannot use more than 27 component devices Date: Sat, 25 Feb 2017 23:30:03 +0000 Message-ID: <58B2137B.6070608@youngman.org.uk> References: <20170224040816.41f2f372.ian_bruce@mail.ru> <41ea334c-ae1c-dac6-e1a1-480d3700a588@turmel.org> <20170224084024.4dfe83a2.ian_bruce@mail.ru> <1e40da0d-b175-9ff5-d2e5-cf1f25aacc26@turmel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Phil Turmel , ian_bruce@mail.ru, linux-raid@vger.kernel.org List-Id: linux-raid.ids On 25/02/17 22:00, Phil Turmel wrote: >> This is all a rather important usage of raid, actually, imho. It >> > seems so obvious - create a temporary mirror, wait for the sync to >> > complete, suspend i/o to get the disk consistent, then you can break >> > the mirror and carry on. Terabytes :-) of data safely backed up in >> > the space of seconds. > No. Don't go there. There's already a technology out there that does > this correctly, called LVM snapshots. And they let you resume normal > operations after a very brief hesitation, and the snapshot holds the > static image while you copy it off. Will it let you put that snapshot on a hot-plug disk you can remove? For my little system I'd quite happily mirror it off onto a hard-disk and unplug it. Oh - and I'm not running lvm. Not that I think there's anything wrong with that, it's just yet another layer that I'm not (currently) comfortable with. Is there a sound technical reason not to go there, or is it simply a case of "learn another tool for that job"? The less tools I have to know the better, imho. (Although why I'm worrying, I don't know. I know btrfs is planning to make that obsolete :-) Cheers, Wol