Re: Ceph rdb question about possibilities

[Jan Schermer <jan@xxxxxxxxxxx>]

Yum repo doesn't really sound like something "mission critical" (in my experience). You need to wait for the repo to update anyway before you can use the package, so not something realtime either.

CephFS is overkill for this.

I would either simply rsync the repo between the three machines via cron (and set DNS to point to all three IPs they have). If you need something "more realtime" than you can use for example incron.

Or you can push new packages to all three and refresh them (assuming you have some tools that do that already).

Or if you want to use Ceph then you can create one rbd image that only gets mounted on one of the hosts, and if that goes down you remount it elsewhere (by hand, or via pacemaker, cron script...). I don't think Ceph makes sense if that going to be the only use, though...

Maybe you could also push the packages to RadosGW, but I'm not familiar with it that much, not sure how you build a repo that points there. This would make sense but I have no idea if it's simple to do.

Jan

On 28 Jan 2016, at 13:03, Sándor Szombat <szombat.sandor@xxxxxxxxx> wrote:

Hello,

yes I missunderstand things I things. Thanks for your help!

So the situation is next: We have a yum repo with rpm packages. We want to store these rpm's in Ceph. But we have three main node what can be able to install the other nodes. So we have to share these rpm packages between the three host. I check the CephFs, it will be the best solution for us, but it is in beta and beta products cant allowed for us. This is why I tryto find another, Ceph based solution. 

2016-01-28 12:46 GMT+01:00 Jan Schermer <jan@xxxxxxxxxxx>:

This is somewhat confusing.

CephFS is a shared filesystem - you mount that on N hosts and they can access the data simultaneously.
RBD is a block device, this block device can be accesses from more than 1 host, BUT you need to use a cluster aware filesystem (such as GFS2, OCFS).

Both CephFS and RBD use RADOS as a backend, which is responsible for data placement, high-availability and so on.

If you explain your scenario more we could suggest some options - do you really need to have the data accessible on more servers, or is a (short) outage acceptable when one server goes down? What type of data do you need to share and how will the data be accessed?

Jan

> On 28 Jan 2016, at 11:06, Sándor Szombat <szombat.sandor@xxxxxxxxx> wrote:
>
> Hello all!
>
> I check the Ceph FS, but it is beta now unfortunatelly. I start to meet with the rdb. It is possible to create an image in a pool, mount it as a block device (for example /dev/rbd0), and format this as HDD, and mount it on 2 host? I tried to make this, and it's work but after mount the  /dev/rbd0 on the two host and I tried to put files into these mounted folders it can't refresh automatically between hosts.
> So the main question: this will be a possible solution?
> (The task: we have 3 main node what can install the other nodes with ansible, and we want to store our rpm's in ceph it is possible. This is necessary because of high avability.)
>
> Thanks for your help!
>

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