Hi，Nigel
I read some PPT document and find that when n (n<M) host get down, the PG become degraded, is it mean that client still could write to the degraded PG even if there not have enough host to hold all the K+M chunks? (like the replicated PG). And if n=M (M host get down), what is state the pg will be ?
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Yueliang
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On June 24, 2015 at 15:10:46, Nigel Williams (nigel.d.williams@xxxxxxxxx) wrote: On Wed, Jun 24, 2015 at 4:29 PM, Yueliang <yueliang9527@xxxxxxxxx> wrote:
> When I use K+M hosts in the EC pool, if M hosts get down, still have K hosts
> active, Can I continue write data to the pool ?
If your CRUSH map specifies a failure-domain at the host level (so no
two chunks share the same host) then you will be unable to write to
the pool. If instead the failure-domain is OSD then with enough OSDs
pool writes would still be accepted.
> Since there only have K
> hosts, not K+M hosts, When client write a data to EC pool , Primary OSD will
> split the data to K data pieces，but how about the M coding pieces? is it
> still be calculated and where it should be hold ?
Same as above, with failure-domain = host then there would be nowhere
to put the M coding pieces.
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