I agree, simplifying "deployment" by adding another layer of complexity does bring much more problems and hard times when something goes wrong in the runtime. Few additional steps at "install phase" and better understanding of underlying architecture, commands, whatever ... have much more pros than cons at the end. Even in the most simplified installation, deployment, systems are complex by itself enough so I have no idea why under the recommended installation method https://docs.ceph.com/en/latest/cephadm/install/ there are lvm, systemd, docker or podman. I suggest that much effort should be put into better and more understandable documentation. Rok On Wed, Jun 2, 2021 at 11:36 AM Matthew Vernon <mv3@xxxxxxxxxxxx> wrote: > Hi, > > In the discussion after the Ceph Month talks yesterday, there was a bit > of chat about cephadm / containers / packages. IIRC, Sage observed that > a common reason in the recent user survey for not using cephadm was that > it only worked on containerised deployments. I think he then went on to > say that he hadn't heard any compelling reasons why not to use > containers, and suggested that resistance was essentially a user > education question[0]. > > I'd like to suggest, briefly, that: > > * containerised deployments are more complex to manage, and this is not > simply a matter of familiarity > * reducing the complexity of systems makes admins' lives easier > * the trade-off of the pros and cons of containers vs packages is not > obvious, and will depend on deployment needs > * Ceph users will benefit from both approaches being supported into the > future > > We make extensive use of containers at Sanger, particularly for > scientific workflows, and also for bundling some web apps (e.g. > Grafana). We've also looked at a number of container runtimes (Docker, > singularity, charliecloud). They do have advantages - it's easy to > distribute a complex userland in a way that will run on (almost) any > target distribution; rapid "cloud" deployment; some separation (via > namespaces) of network/users/processes. > > For what I think of as a 'boring' Ceph deploy (i.e. install on a set of > dedicated hardware and then run for a long time), I'm not sure any of > these benefits are particularly relevant and/or compelling - Ceph > upstream produce Ubuntu .debs and Canonical (via their Ubuntu Cloud > Archive) provide .debs of a couple of different Ceph releases per Ubuntu > LTS - meaning we can easily separate out OS upgrade from Ceph upgrade. > And upgrading the Ceph packages _doesn't_ restart the daemons[1], > meaning that we maintain control over restart order during an upgrade. > And while we might briefly install packages from a PPA or similar to > test a bugfix, we roll those (test-)cluster-wide, rather than trying to > run a mixed set of versions on a single cluster - and I understand this > single-version approach is best practice. > > Deployment via containers does bring complexity; some examples we've > found at Sanger (not all Ceph-related, which we run from packages): > > * you now have 2 process supervision points - dockerd and systemd > * docker updates (via distribution unattended-upgrades) have an > unfortunate habit of rudely restarting everything > * docker squats on a chunk of RFC 1918 space (and telling it not to can > be a bore), which coincides with our internal network... > * there is more friction if you need to look inside containers > (particularly if you have a lot running on a host and are trying to find > out what's going on) > * you typically need to be root to build docker containers (unlike > packages) > * we already have package deployment infrastructure (which we'll need > regardless of deployment choice) > > We also currently use systemd overrides to tweak some of the Ceph units > (e.g. to do some network sanity checks before bringing up an OSD), and > have some tools to pair OSD / journal / LVM / disk device up; I think > these would be more fiddly in a containerised deployment. I'd accept > that fixing these might just be a SMOP[2] on our part. > > Now none of this is show-stopping, and I am most definitely not saying > "don't ship containers". But I think there is added complexity to your > deployment from going the containers route, and that is not simply a > "learn how to use containers" learning curve. I do think it is > reasonable for an admin to want to reduce the complexity of what they're > dealing with - after all, much of my job is trying to automate or > simplify the management of complex systems! > > I can see from a software maintainer's point of view that just building > one container and shipping it everywhere is easier than building > packages for a number of different distributions (one of my other hats > is a Debian developer, and I have a bunch of machinery for doing this > sort of thing). But it would be a bit unfortunate if the general thrust > of "let's make Ceph easier to set up and manage" was somewhat derailed > with "you must use containers, even if they make your life harder". > > I'm not going to criticise anyone who decides to use a container-based > deployment (and I'm sure there are plenty of setups where it's an > obvious win), but if I were advising someone who wanted to set up and > use a 'boring' Ceph cluster for the medium term, I'd still advise on > using packages. I don't think this makes me a luddite :) > > Regards, and apologies for the wall of text, > > Matthew > > [0] I think that's a fair summary! > [1] This hasn't always been true... > [2] Simple (sic.) Matter of Programming > > > -- > The Wellcome Sanger Institute is operated by Genome Research > Limited, a charity registered in England with number 1021457 and a > company registered in England with number 2742969, whose registered > office is 215 Euston Road, London, NW1 2BE. > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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