I think it would suffice to change rule 0 to use a device class as well, as you already mentioned yourself. Do you have pools that use that rule? If not, the change wouldn’t even have any impact. Zitat von Dave Hall <kdhall@binghamton.edu>:
Oddly, the Nautilus cluster that I'm gradually decommissioning seems to have the same shadow root pattern in its crush map. I don't know if that really means anything, but at least I know it's not something I did differently when I set up the new Reef cluster.
-Dave
-- Dave Hall Binghamton University kdhall@binghamton.edu
On Fri, Sep 20, 2024 at 12:48 PM Dave Hall <kdhall@binghamton.edu> wrote:
Stefan, Anthony,
Anthony's sequence of commands to reclassify the root failed with errors. so I have tried to look a little deeper.
I can now see the extra root via 'ceph osd crush tree --show-shadow'. Looking at the decompiled crush tree, I can also see the extra root:
root default { id -1 # do not change unnecessarily
* id -2 class hdd # do not change unnecessarily* # weight 361.90518 alg straw2 hash 0 # rjenkins1 item ceph00 weight 90.51434 item ceph01 weight 90.29265 item ceph09 weight 90.80554 item ceph02 weight 90.29265 }
Based on the hints given in the link provided by Stefan, it would appear that the correct solution might be to get rid of 'id -2' and change id -1 to class hdd,
root default {
* id -1 class hdd # do not change unnecessarily* # weight 361.90518 alg straw2 hash 0 # rjenkins1 item ceph00 weight 90.51434 item ceph01 weight 90.29265 item ceph09 weight 90.80554 item ceph02 weight 90.29265 }
but I'm no expert and anxious about losing data.
The rest of the rules in my crush map are:
# rules rule replicated_rule { id 0 type replicated step take default step chooseleaf firstn 0 type host step emit } rule block-1 { id 1 type erasure step set_chooseleaf_tries 5 step set_choose_tries 100 step take default class hdd step choose indep 0 type osd step emit } rule default.rgw.buckets.data { id 2 type erasure step set_chooseleaf_tries 5 step set_choose_tries 100 step take default class hdd step choose indep 0 type osd step emit } rule ceph-block { id 3 type erasure step set_chooseleaf_tries 5 step set_choose_tries 100 step take default class hdd step choose indep 0 type osd step emit } rule replicated-hdd { id 4 type replicated step take default class hdd step choose firstn 0 type osd step emit }
# end crush map
Of these, the last - id 4 - is one that I added while trying to figure this out. What this tells me is that the 'take' step in rule id 0 should probably change to 'step take default class hdd'.
I also notice that each of my host stanzas (buckets) has what looks like two roots. For example
host ceph00 { id -3 # do not change unnecessarily id -4 class hdd # do not change unnecessarily # weight 90.51434 alg straw2 hash 0 # rjenkins1 item osd.0 weight 11.35069 item osd.1 weight 11.35069 item osd.2 weight 11.35069 item osd.3 weight 11.35069 item osd.4 weight 11.27789 item osd.5 weight 11.27789 item osd.6 weight 11.27789 item osd.7 weight 11.27789 }
I assume I may need to clean this up somehow, or perhaps this is the real problem.
Please advise.
Thanks.
-Dave
-- Dave Hall Binghamton University kdhall@binghamton.edu
On Thu, Sep 19, 2024 at 3:56 AM Stefan Kooman <stefan@bit.nl> wrote:
On 19-09-2024 05:10, Anthony D'Atri wrote:
Anthony,
So it sounds like I need to make a new crush rule for replicated pools
that specifies default-hdd and the device class? (Or should I go the other way around? I think I'd rather change the replicated pools even though there's more of them.)
I think it would be best to edit the CRUSH rules in-situ so that each
specifies the device class, that way if you do get different media in the future, you'll be ready. Rather than messing around with new rules and modifying pools, this is arguably one of the few times when one would decompile, edit, recompile, and inject the CRUSH map in toto.
I haven't tried this myself, but maybe something like the below, to
avoid the PITA and potential for error of edting the decompiled text file by hand.
ceph osd getcrushmap -o original.crush crushtool -d original.crush -o original.txt crushtool -i original.crush --reclassify --reclassify-root default hdd
--set-subtree-class default hdd -o adjusted.crush
crushtool -d adjusted.crush -o adjusted.txt crushtool -i original.crush --compare adjusted.crush ceph osd setcrushmap -i adjusted.crush
This might be of use as well (if a lot of data would move): https://blog.widodh.nl/2019/02/comparing-two-ceph-crush-maps/
Gr. Stefan
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