Hi,
Actually I've learned that it's not needed for a rule to start with a root
bucket, so I can heve rules that will only consider a subtree of my total
resources, and achieve what I was trying to do with the different disjunct
hierarchies.
BTW: it is possible to have different trees with different roots, with some
OSDs being part of multiple such trees, and create different rules that will
start with one root or the other. But I was told that this could mess up the
calculation for pg autoscaler and other housekeeping functions. So it seems a
better option to have each OSD in one single tree, and use rules that will only
consider subtrees ...
Regards,
Laszlo
Date: Mon, 19 Jun 2023 07:41:35 +0000
From: Eugen Block<[email protected]>
Subject: [ceph-users] Re: same OSD in multiple CRUSH hierarchies
To:[email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=utf-8; format=flowed; DelSp=Yes
Hi,
I don't think this is going to work. Each OSD belongs to a specific
host and you can't have multiple buckets (e.g. bucket type "host")
with the same name in the crush tree. But if I understand your
requirement correctly, there should be no need to do it this way. If
you structure your crush tree according to your separation
requirements and the critical pools use designated rules, you can
still have a rule that doesn't care about the data separation but
distributes the replicas across the available hosts (given your
failure domain would be "host"), which is already the default for the
replicated_rule. Did I misunderstand something?
Regards,
Eugen
Zitat von Budai Laszlo<[email protected]>:
Hi there,
I'm curious if there is anything against configuring an ODS to be
part in multiple CRUSH hierarchies. I'm thinking of the following
scenario:
I want to create pools that are using distinct sets of OSDs. I want
to make sure that a piece data which replicated at application level
will not end up on the same OSD. So I would creat multiple CRUSH
hierarchies (root - host - osd) but using different OSDs in each,
and different rules that are using those hierarchies. Then I would
create pools with the different rules, and use those different pools
for storing the data for the different application instances. But I
would also like to use the OSDs in the "default hierarchy" set up by
ceph where all the hosts are in the same root bucket, and have the
default replicated rule, so my generic data volumes would be able to
spread across all the OSDs available.
Is there something against this setup?
Thank you for any advice!
Laszlo
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