On 2019-08-31 06:02, Konstantin Shalygin wrote:
On 8/31/19 3:42 AM, Zoltan Arnold Nagy wrote:
Originally our osd tree looked like this:
ID CLASS WEIGHT TYPE
NAME STATUS REWEIGHT PRI-AFF
-1 2073.15186 root default
-14 176.63100 rack s01-rack
-19 176.63100 host s01
<snip osds>
-15 171.29900 rack s02-rack
-20 171.29900 host s02
<snip osds>
etc. You get the idea. It was a legacy thing as we've been upgrading
this cluster
since probably firefly, and started with way less hardware.
The crush rule was set up like this originally:
step take default
step chooseleaf firstn 0 type rack
which we have modified to
step take default
step chooseleaf firstn 0 type host
taking advantage of chooseleaf's behavior (eg searching in depth
instead of just
a single level).
Now we thought we could get rid of the rack buckets simply by moving
the
host buckets to the root using "ceph osd crush move s01 root=default",
however
this resulted in a bunch of data movement.
Swapping the IDs manually in the crushmap seems to work (verified via
crushtool's
--compare), eg. changing the ID of s01 to s01-rack's and vice versa,
including
all shadow trees.
Looking around I saw that there is a swap-bucket command but that does
not swap
the IDs just bucket contents, so would result in data movement.
Other than manually editing the crushmap is there a better way to
achieve this?
Is this way the most optimal?
If you are on Luminous+ version - upmap.
Could you elaborate a bit more? upmap is used to map specific PGs to
specific OSDs
in order to deal with CRUSH inefficiencies.
Why would I want to add a layer of indirection when the goal is to
remove the bucket
entirely?
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