yes you can. but just like a raid5 array with a lost disk, it is not a
comfortable way to run your cluster for any significant time. you also
get performance degradations.
having a warning active all the time makes it harder to detect new
issues, and such. One becomes numb to the warning allways beeing on.
strive to have your cluster in health ok all the time. and design so
that you have the fault tolerance you want as overhead. having more
nodes then strictly needed allow ceph to self heal quickly. and also
gives better performance, by spreading load over more machines.
10+4 on 14 nodes means each and every nodes are hit on each write.
kind regards
Ronny Aasen
On 23. okt. 2017 21:12, Jorge Pinilla López wrote:
I have one question, what can or can't do a cluster working on degraded
mode?
With K=10 + M = 4 if one of my OSDs node fails it will start working on
degraded mode, but can I still do writes and reads from that pool?
El 23/10/2017 a las 21:01, Ronny Aasen escribió:
On 23.10.2017 20:29, Karun Josy wrote:
Hi,
While creating a pool with erasure code profile k=10, m=4, I get PG
status as
"200 creating+incomplete"
While creating pool with profile k=5, m=3 it works fine.
Cluster has 8 OSDs with total 23 disks.
Is there any requirements for setting the first profile ?
you need K+M+X osd nodes. K and M comes from the profile, X is how
many nodes you want to be able to tolerate failure of, without
becoming degraded. (how many failed nodes ceph should be able to
automatically heal)
so with K=10 + M = 4 you need minimum 14 nodes and you have 0 fault
tolerance (a single failure = a degreded cluster) so you have to
scramble to replace the node to get HEALTH OK again. if you have 15
nodes you can loose 1 node and cehp will automatically rebalance to
the 14 needed nodes, and you can replace the lost node at your leisure.
kind regards
Ronny Aasen
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--
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*Jorge Pinilla López*
jorpilo@xxxxxxxxx
Estudiante de ingenieria informática
Becario del area de sistemas (SICUZ)
Universidad de Zaragoza
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