ceph osd replacement with shared journal device

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On Mon, 29 Sep 2014, Dan Van Der Ster wrote:
> Hi Owen,
> 
> > On 29 Sep 2014, at 10:33, Owen Synge <osynge at suse.com> wrote:
> > 
> > Hi Dan,
> > 
> > At least looking at upstream to get journals and partitions persistently
> > working, this requires gpt partitions, and being able to add a GPT
> > partition UUID to work perfectly with minimal modification.
> > 
> > I am not sure the status of this on RHEL6, The latest Fedora and
> > OpenSUSE support this but SLE12 (To be released) and I think RHEL7 do
> > support this.
> > 
> > Im sure you can bypass this as every data partition contains a symlink
> > to the journal partition, but persistent naming may be more work if you
> > dont use GPT partitions.
> 
> The persistent names and udev triggers all work when I first setup the drives with ceph-disk. The ptables are indeed GPT and the links to the journals are to the persistent by-partuuid links. My setup is like this, and it works perfectly:
> 
> ceph-disk prepare /dev/sde /dev/sda
> ceph-disk prepare /dev/sdf /dev/sda
> ceph-disk prepare /dev/sdg /dev/sda
> ceph-disk prepare /dev/sdh /dev/sda
> ceph-disk prepare /dev/sdi /dev/sda
> 
> (each time ceph-disk creates the next partition on sda and creates the correct persistent links. The udev trigger calls ceph-disk activate and the OSD is eventually started).
> 
> My only question is about the replacement procedure (e.g. for sde). The options I?ve seen are
>   - ceph-disk prepare /dev/sde /dev/sda  ? this will create a 6th partition on sda
>   - ceph-disk prepare /dev/sde /dev/sda1  ? in this case the journal link is to sda1 instead of the persistent link.

I think the thing we should fix is for the /dev/sda1 user-provided path to 
be resolved to a /dev/disk/... path.  Unless someone can think of a case 
where the user *wouldn't* want that resolution to happen?

sage


>   - parted /dev/sda rm 1; ceph-disk prepare /dev/sde /dev/sda ? I thought this was working, but in fact the ptable looks like this afterwards (part #1 is at the end of the disk):
> 
> Number  Start   End     Size    File system  Name          Flags
>  2      21.5GB  43.0GB  21.5GB               ceph journal
>  3      43.0GB  64.4GB  21.5GB               ceph journal
>  4      64.4GB  85.9GB  21.5GB               ceph journal
>  5      85.9GB  107GB   21.5GB               ceph journal
>  1      107GB   129GB   21.5GB               ceph journal
> 
> I?m going to trace what is happening with ceph-disk prepare /dev/sde /dev/sda1 and try to coerce that to use the persistent name.
> 
> Cheers, Dan
> 
> 
> 
> 
> 
> > 
> > Best of luck.
> > 
> > Owen
> > 
> > 
> > 
> > 
> > 
> > On 09/29/2014 10:24 AM, Dan Van Der Ster wrote:
> >> Hi,
> >> 
> >>> On 29 Sep 2014, at 10:01, Daniel Swarbrick <daniel.swarbrick at profitbricks.com> wrote:
> >>> 
> >>> On 26/09/14 17:16, Dan Van Der Ster wrote:
> >>>> Hi,
> >>>> Apologies for this trivial question, but what is the correct procedure to replace a failed OSD that uses a shared journal device?
> >>>> 
> >>>> I?m just curious, for such a routine operation, what are most admins doing in this case?
> >>>> 
> >>> 
> >>> I think ceph-osd is what you need.
> >>> 
> >>> ceph-osd -i <osd id> ?mkjournal
> >> 
> >> 
> >> At the moment I am indeed using this command to in our puppet manifests for creating and replacing OSDs. But now I?m trying to use the ceph-disk udev magic, since it seems to be the best (perhaps only?) way to get persistently named OSD and journal devs (on RHEL6).
> >> 
> >> Cheers, Dan
> >> _______________________________________________
> >> ceph-users mailing list
> >> ceph-users at lists.ceph.com
> >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> >> 
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> 
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