From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Stroetmann Subject: Re: [RFC PATCH 0/5] Btrfs: Add hot data tracking functionality Date: Thu, 29 Jul 2010 15:17:13 +0200 Message-ID: <4C517F59.5060507@ontolinux.com> References: <1280268023-18408-1-git-send-email-bchociej@gmail.com> <4C4F6DF2.6090905@ontolinux.com> <1280354448.7694.4.camel@mingming-laptop> <20100729121729.GK655@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: Dave Chinner , Minming Cao , linux-kernel , linux-fsdevel Return-path: In-Reply-To: <20100729121729.GK655@dastard> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Aloha Mingming, Aloha Dave; On the 29.07.2010 14:17, Dave Chinner wrote: > On Wed, Jul 28, 2010 at 03:00:48PM -0700, Mingming Cao wrote: > >> On Wed, 2010-07-28 at 01:38 +0200, Christian Stroetmann wrote: >> >>> At the 28.07.2010 00:00, Ben Chociej wrote: >>> Wouldn't this feature be useful for other file systems as well, so that >>> a more general and not an only Btrfs related solution is preferable? >>> >>> >> Would certainly nice to add this feature to all filesystem, but right >> now btrfs is the only fs which have multiple device support in itself. >> > Thanks for your explanation, Mingming. And I had further questions to this point, but didn't know exactly how to formulate them in a short way. But luckily Dave has a possible solution that is related with my questions around the multiple device feature of Btrfs and hot data handling. > Why does it even need multiple devices in the filesystem? Yes, that was the point I asked myself after reading about this in the Btrfs wiki (https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices) and how ZFS does it. > All the > filesystem needs to know is the relative speed of regions of it's > block address space and to be provided allocation hints. everything > else is just movement of data. You could keep the speed information > in the device mapper table and add an interface for filesystems to > query it, and then you've got infrastructure that all filesystems > could hook into. > Yes indeed, something like this general solution that doesn't need the multiple device feature at all. > The tracking features dont' appear to have anything btrfs specific > in them, so t iseems wrong to implement it there just because you're > only looking at btrfs' method of tracking multiple block devices > and moving blocks.... > > Cheers, > > Dave. > Thank you very much for being creative. :D Cheerio Christian *<:o) O>-< -(D)>-<