Re: how possible is that ceph cluster crash

[Nick Fisk <nick@xxxxxxxxxx>]

Yes, because these things happen

http://www.theregister.co.uk/2016/11/15/memset_power_cut_service_interruption/

We had customers who had kit in this DC.

To use your analogy, it's like crossing the road at traffic lights but  
not checking cars have stopped. You might be OK 99%of the time, but  
sooner or later it will bite you in the arse and it won't be pretty.

________________________________
From: "Brian ::" <bc@xxxxxxxx>
Sent: 18 Nov 2016 11:52 p.m.
To: sjust@xxxxxxxxxx
Cc: Craig Chi; ceph-users@xxxxxxxxxxxxxx; Nick Fisk
Subject: Re:  how possible is that ceph cluster crash

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> This is like your mother telling not to cross the road when you were 4
> years of age but not telling you it was because you could be flattened
> by a car :)
>
> Can you expand on your answer? If you are in a DC with AB power,
> redundant UPS, dual feed from the electric company, onsite generators,
> dual PSU servers, is it still a bad idea?
>
>
>
>
> On Fri, Nov 18, 2016 at 6:52 PM, Samuel Just <sjust@xxxxxxxxxx> wrote:
> > Never *ever* use nobarrier with ceph under *any* circumstances.  I
> > cannot stress this enough.
> > -Sam
> >
> > On Fri, Nov 18, 2016 at 10:39 AM, Craig Chi <craigchi@xxxxxxxxxxxx> wrote:
> > > Hi Nick and other Cephers,
> > >
> > > Thanks for your reply.
> > >
> > > > 2) Config Errors
> > > > This can be an easy one to say you are safe from. But I would say most
> > > > outages and data loss incidents I have seen on the mailing
> > > > lists have been due to poor hardware choice or configuring options such as
> > > > size=2, min_size=1 or enabling stuff like nobarriers.
> > >
> > > I am wondering the pros and cons of the nobarrier option used by Ceph.
> > >
> > > It is well known that nobarrier is dangerous when power outage happens, but
> > > if we already have replicas in different racks or PDUs, will Ceph  
> > > reduce the
> > > risk of data lost with this option?
> > >
> > > I have seen many performance tuning articles providing nobarrier option in
> > > xfs, but there are not many of then mention the trade-off of nobarrier.
> > >
> > > Is it really unacceptable to use nobarrier in production  
> > > environment? I will
> > > be much grateful if you guys are willing to share any experiences about
> > > nobarrier and xfs.
> > >
> > > Sincerely,
> > > Craig Chi (Product Developer)
> > > Synology Inc. Taipei, Taiwan. Ext. 361
> > >
> > > On 2016-11-17 05:04, Nick Fisk <nick@xxxxxxxxxx> wrote:
> > >
> > > > -----Original Message-----
> > > > From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of
> > > > Pedro Benites
> > > > Sent: 16 November 2016 17:51
> > > > To: ceph-users@xxxxxxxxxxxxxx
> > > > Subject:  how possible is that ceph cluster crash
> > > >
> > > > Hi,
> > > >
> > > > I have a ceph cluster with 50 TB, with 15 osds, it is working fine for one
> > > > year and I would like to grow it and migrate all my old
> > > storage,
> > > > about 100 TB to ceph, but I have a doubt. How possible is that the cluster
> > > > fail and everything went very bad?
> > >
> > > Everything is possible, I think there are 3 main risks
> > >
> > > 1) Hardware failure
> > > I would say Ceph is probably one of the safest options in regards to
> > > hardware failures, certainly if you start using 4TB+ disks.
> > >
> > > 2) Config Errors
> > > This can be an easy one to say you are safe from. But I would say most
> > > outages and data loss incidents I have seen on the mailing
> > > lists have been due to poor hardware choice or configuring options such as
> > > size=2, min_size=1 or enabling stuff like nobarriers.
> > >
> > > 3) Ceph Bugs
> > > Probably the rarest, but potentially the most scary as you have less
> > > control. They do happen and it's something to be aware of
> > >
> > > How reliable is ceph?
> > > > What is the risk about lose my data.? is necessary backup my data?
> > >
> > > Yes, always backup your data, no matter solution you use. Just like RAID !=
> > > Backup, neither does ceph.
> > >
> > > > Regards.
> > > > Pedro.
> > > > _______________________________________________
> > > > 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
> > >
> > >
> > >
> > >
> > > Sent from Synology MailPlus
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