----- Mail original ----- > De: "David" <david@xxxxxxxxxx> > À: "ceph-users" <ceph-users@xxxxxxxxxxxxxx> > Envoyé: Dimanche 4 Juin 2017 17:59:55 > Objet: Re: CEPH backup strategy and best practices > 4 juni 2017 kl. 23:23 skrev Roger Brown < [ mailto:rogerpbrown@xxxxxxxxx | > rogerpbrown@xxxxxxxxx ] >: > > I'm a n00b myself, but I'll go on record with my understanding. > > On Sun, Jun 4, 2017 at 3:03 PM Benoit GEORGELIN - yulPa < [ > mailto:benoit.georgelin@xxxxxxxx | benoit.georgelin@xxxxxxxx ] > wrote: > > BQ_BEGIN > > Hi ceph users, > > Ceph have a very good documentation about technical usage, but there is a lot of > conceptual things missing (from my point of view) > It's not easy to understand all at the same time, but yes, little by little it's > working. > > Here are some questions about ceph , hope someone can take a little time to > point me where I can find answers : > > - Backup : > Do you backup data from a CEPH cluster or you consider a copy as a backup of > that file ? > Let's say I have replica size of 3 . Somehow , my crush map will keep 2 copy in > my main rack and 1 copy to another rack in another datacenter > Can I consider the third copy as a backup ? What would be your position ? > > > > > Replicas are not backups. Just ask GitLab after accidental deletion. source: [ > https://www.theregister.co.uk/2017/02/01/gitlab_data_loss/ | > https://www.theregister.co.uk/2017/02/01/gitlab_data_loss/ ] > > > BQ_BEGIN > > > - Writing process of ceph object storage using radosgw > Simple question, but not sure about it. > The more replica the more slower will be my cluster ? Does CEPH have to > acknowledge the number of replica before saying it's good ? > From what I read, CEPH will write and acknowledge the de primary OSD of the pool > , So if that the cas, I does not matter how many replica I want and how far are > situated the others OSD that would work the same. > Can I chose myseft the primary OSD in my zone 1 , have a copy on zone 2 (same > rack) and a third zone 3 in another datacenter that might have some latency . > > BQ_END > > > More replicas make slower cluster because it waits for all devices to > acknowledge write before reporting back. source: ? > > BQ_END > > > I’d say stick with 3 replicas in one DC, then if you want to add another DC for > better data protection (note, not backup), you’ll just add asynchronous > mirroring between DCs ( [ http://docs.ceph.com/docs/master/rbd/rbd-mirroring/ | > http://docs.ceph.com/docs/master/rbd/rbd-mirroring/ ] ) with another cluster > there. > That way you’ll have a quick cluster (especially if you use awesome disks like > NVME SSD journals + SSD storage or better) with a location redundancy. > > > BQ_BEGIN > > > > BQ_BEGIN > > > - Data persistance / availability > If crush map is by hosts and I have 3 hosts with replication of 3 > This means , I will have 1 copy on each hosts > Does it means I can lost 2 hosts and still have my cluster working, at least on > read mode ? and eventually in write too if i say , osd pool default min size = > 1 > > BQ_END > > > Yes, I think. But best practice is to have at least 5 hosts (N+2) so you can > lose 2 hosts and still keep 3 replicas. > > BQ_END > > > Keep in mind that you ”should” have enough storage free as well to be able to > loose 2 nodes. If you fill 5 nodes to 80% and loose 2 nodes you won’t be able > to repair it all until you get them up and running again. > This apply only if you crush map is just OSD and not HOST right ? Because if I have 5 NODES, replica 3 and all nodes are 80% used , if i loose 2 nodes, I still have 3 Nodes up at 80%, the cluster should be told not to recover the copies missing.. that the only thing > > > > > > > Thanks for your help. > - > > Benoît G > _______________________________________________ > ceph-users mailing list > [ mailto:ceph-users@xxxxxxxxxxxxxx | ceph-users@xxxxxxxxxxxxxx ] > [ http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com | > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com ] > BQ_END > > > Roger > _______________________________________________ > ceph-users mailing list > [ mailto:ceph-users@xxxxxxxxxxxxxx | ceph-users@xxxxxxxxxxxxxx ] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > BQ_END > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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