From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Pilcher Subject: Re: [RFC] zodcache - auto-start dm-cache devices Date: Fri, 18 Dec 2015 10:55:32 -0600 Message-ID: References: <22132.12088.729694.12882@quad.stoffel.home> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <22132.12088.729694.12882@quad.stoffel.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids On 12/18/2015 10:07 AM, John Stoffel wrote: >>>From my reading of the docs, it's clear that zodcache is lower down > the stack than LVMcache, but higher than bcache. I would actually say that zodcache is at about the same level as bcache. The main conceptual difference is that zodcache does device probing/recognition and setup are done in userspace, where bcache does it in kernel space. (I.e. echo the device name to /sys/fs/bcache/register and the kernel looks a the device, decides what it is, etc.) > So describinng how your setup can provide a central cache pool across > multiple VGs would be awesome, but it's not quite clear to me that you > can do this in reality without doing multiple layers of block devices. Currently you'll need multiple zodcache devices to create multiple VGs. It should be possible to make these devices partitionable with a udev rule that calls kpartx as appropriate. > And since I'm paranoid (to a degree!) about resiliency, mirroring the > cache devices is a critical part for me. I haven't yet tested zodcache on top of MD RAID, but I fully expect it to work. > Also, I'm on debian, so that's another piece of documentation that's > kinda sorta missing. What do you need beyond what's in section III-B of the README? -- ======================================================================== Ian Pilcher arequipeno@gmail.com -------- "I grew up before Mark Zuckerberg invented friendship" -------- ========================================================================