[ceph-users] Running Jewel and Luminous mixed for a longer period

Wido den Hollander wido at 42on.com
Wed Dec 6 01:21:43 PST 2017


> Op 6 december 2017 om 10:17 schreef Caspar Smit <casparsmit at supernas.eu>:
> 
> 
> 2017-12-05 18:39 GMT+01:00 Richard Hesketh <richard.hesketh at rd.bbc.co.uk>:
> 
> > On 05/12/17 17:10, Graham Allan wrote:
> > > On 12/05/2017 07:20 AM, Wido den Hollander wrote:
> > >> Hi,
> > >>
> > >> I haven't tried this before but I expect it to work, but I wanted to
> > >> check before proceeding.
> > >>
> > >> I have a Ceph cluster which is running with manually formatted
> > >> FileStore XFS disks, Jewel, sysvinit and Ubuntu 14.04.
> > >>
> > >> I would like to upgrade this system to Luminous, but since I have to
> > >> re-install all servers and re-format all disks I'd like to move it to
> > >> BlueStore at the same time.
> > >
> > > You don't *have* to update the OS in order to update to Luminous, do
> > you? Luminous is still supported on Ubuntu 14.04 AFAIK.
> > >
> > > Though obviously I understand your desire to upgrade; I only ask because
> > I am in the same position (Ubuntu 14.04, xfs, sysvinit), though happily
> > with a smaller cluster. Personally I was planning to upgrade ours entirely
> > to Luminous while still on Ubuntu 14.04, before later going through the
> > same process of decommissioning one machine at a time to reinstall with
> > CentOS 7 and Bluestore. I too don't see any reason the mixed Jewel/Luminous
> > cluster wouldn't work, but still felt less comfortable with extending the
> > upgrade duration.
> > >
> > > Graham
> >
> > Yes, you can run luminous on Trusty; one of my clusters is currently
> > Luminous/Bluestore/Trusty as I've not had time to sort out doing OS
> > upgrades on it. I second the suggestion that it would be better to do the
> > luminous upgrade first, retaining existing filestore OSDs, and then do the
> > OS upgrade/OSD recreation on each node in sequence. I don't think there
> > should realistically be any problems with running a mixed cluster for a
> > while but doing the jewel->luminous upgrade on the existing installs first
> > shouldn't be significant extra effort/time as you're already predicting at
> > least two months to upgrade everything, and it does minimise the amount of
> > change at any one time in case things do start going horribly wrong.
> >
> > Also, at 48 nodes, I would've thought you could get away with cycling more
> > than one of them at once. Assuming they're homogenous taking out even 4 at
> > a time should only raise utilisation on the rest of the cluster to a little
> > over 65%, which still seems safe to me, and you'd waste way less time
> > waiting for recovery. (I recognise that depending on the nature of your
> > employment situation this may not actually be desirable...)
> >
> >
> Assuming size=3 and min_size=2 and failure-domain=host:
> 
> I always thought that bringing down more then 1 host cause data
> inaccessebility right away because the chance that a pg will have osd's in
> these 2 hosts is there. Only if the failure-domain is higher then host
> (rack or something) you can safely bring more then 1 host down (in the same
> failure domain offcourse).
> 
> Am i right?

Yes, you are right. This cluster in this case has failure domain set to 'rack' and thus allows for multiple machines in one rack to go down without impacting availability.

> 
> Kind regards,
> Caspar
> 
> 
> > Rich
> >
> >
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> >
> >
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