Hello ceph people,
My situation is this: my Ceph cluster is distributed over multiple
sites. The links between sites are rather slow. :-/
Storing one copy of a file at each site should not be a problem with
a reasonable crushmap, but ..:
* how can I verify on which devices a file is stored?
* is it possible to teach clients to read/write from "their", i.e.
the local site's, copy of a file, instead of pulling stuff from
a remote site? Or does ceph notice the speed difference by itself?
* My crushmap looks like this:
type 0 device
type 1 host
type 2 site
type 3 root
... (root => 2 sites => 2 hosts each => 3 devices each)
rule data {
ruleset 0
type replicated
min_size 2
max_size 2
step take root
step chooseleaf firstn 2 type site
step emit
}
but when only one site is reachable, will there be one or two
copies of a file? If the former, how do I fix that? If the latter,
will the copy be redistributed when (the link to) the second site
comes back?
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