The simple (to me, anyway) answer is "if your data is that important, spend the money to insure it". A few hundred $$$, even over a couple hundred systems, is still good policy so far as I'm concerned, when you weigh the possible costs of not being able to access the data versus the cost of a power supply. -----Original Message----- From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Wido den Hollander Sent: Thursday, October 30, 2014 8:54 AM To: ceph-users@xxxxxxxxxxxxxx Subject: Re: Redundant Power Supplies On 10/30/2014 03:36 PM, Nick Fisk wrote: > What's everyone's opinions on having redundant power supplies in your > OSD nodes? > > > > One part of me says let Ceph do the redundancy and plan for the > hardware to fail, the other side says that they are probably worth > having as they lessen the chance of losing a whole node. > > > > Considering they can add £200-300 to a server, the cost can add up > over a number of nodes. > > > > My worst case scenario is where you have dual power feeds A and B. In > this scenario if power feed B ever goes down (fuse/breaker maybe) > then suddenly half your cluster could disappear and start doing > massive recovery operations. I guess this could be worked around by > setting some sort of sub tree limit grouped by power feed. > > > Thoughts? > I did a deployment with single power supplies because of the reasoning you mention. Each rack (3 in total) is split into 3 zones, each zone has it's own switch. In the rack there are 6 machines on powerfeed A together with a switch. A set of machines on B with a switch and there also is a STS switch which provides "powerfeed C". Should a breaker trip in a cabinet we'll loose 6 machines at max. If powerfeed A or B goes down datacenter wide we'll loose 1/3 of the cluster. In the CRUSHMap we defined powerfeeds where we place our replicas over the different powerfeeds. mon_osd_down_out_subtree_limit has been set to "powerfeed" to prevent a whole powerfeed from being marked as "out". This way we saved about EUR 300,00 per machine. On 54 machines that was quite a big save. > > > > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Wido den Hollander 42on B.V. Ceph trainer and consultant Phone: +31 (0)20 700 9902 Skype: contact42on _______________________________________________ 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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