Like many, we have a typical double root crush map, for hdd vs ssd-based
pools. We've been running lumious for some time, so in preparation for a
migration to new storage hardware, I wanted to migrate our pools to use
the new device-class based rules; this way I shouldn't need to
perpetuate the double hdd/ssd crush map for new hardware...
I understand how to migrate our replicated pools, by creating new
replicated crush rules, and migrating them one at a time, but I'm
confused on how to do this for erasure pools.
I can create a new class-aware EC profile something like:
ceph osd erasure-code-profile set ecprofile42_hdd k=4 m=2 crush-device-class=hdd crush-failure-domain=host
then a new crush rule from this:
ceph osd crush rule create-erasure ec42_hdd ecprofile42_hdd
So mostly I want to confirm that is is safe to change the crush rule for
the EC pool. It seems to make sense, but then, as I understand it, you
can't change the erasure code profile for a pool after creation; but
this seems to implicitly do so...
old rule:
rule .rgw.buckets.ec42 {
id 17
type erasure
min_size 3
max_size 20
step set_chooseleaf_tries 5
step take platter
step chooseleaf indep 0 type host
step emit
}
old ec profile:
# ceph osd erasure-code-profile get ecprofile42
crush-failure-domain=host
directory=/usr/lib/x86_64-linux-gnu/ceph/erasure-code
k=4
m=2
plugin=jerasure
technique=reed_sol_van
new rule:
rule ec42_hdd {
id 7
type erasure
min_size 3
max_size 6
step set_chooseleaf_tries 5
step set_choose_tries 100
step take default class hdd
step chooseleaf indep 0 type host
step emit
}
new ec profile:
# ceph osd erasure-code-profile get ecprofile42_hdd
crush-device-class=hdd
crush-failure-domain=host
crush-root=default
jerasure-per-chunk-alignment=false
k=4
m=2
plugin=jerasure
technique=reed_sol_van
w=8
These are both ec42 but I'm not sure why the old rule has "max size 20"
(perhaps because it was generated a long time ago under hammer?).
Thanks for any feedback,
Graham
--
Graham Allan
Minnesota Supercomputing Institute - gta@xxxxxxx
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