Marcel;
To answer your question, I don't see anything that would be keeping these
PGs on the same node. Someone with more knowledge of how the Crush rules
are applied, and the code around these operations, would need to weigh in.
I am somewhat curious though; you define racks, and even rooms in your
tree, but your failure domain is set to host. Is that intentional?
Thank you,
Dominic L. Hilsbos, MBA
Director - Information Technology
Perform Air International, Inc.
DHilsbos(a)PerformAir.com
-----Original Message-----
From: Marcel Kuiper [mailto:ceph@mknet.nl]
Sent: Tuesday, July 21, 2020 10:14 AM
To: ceph-users(a)ceph.io
Cc: Dominic Hilsbos
Subject: Re: [ceph-users] Re: osd out vs crush reweight]
Dominic
The crush rule dump and tree are attached (hope that works). All pools use
crush_rule 1
Marcel
Marcel;
Sorry, could also send the output of:
ceph osd tree
Thank you,
Dominic L. Hilsbos, MBA
Director - Information Technology
Perform Air International, Inc.
DHilsbos(a)PerformAir.com
www.PerformAir.com
-----Original Message-----
From: DHilsbos(a)performair.com [mailto:DHilsbos@performair.com]
Sent: Tuesday, July 21, 2020 9:41 AM
To: ceph(a)mknet.nl; ceph-users(a)ceph.io
Subject: [ceph-users] Re: osd out vs crush reweight]
Marcel;
Thank you for the information.
Could you send the output of:
ceph osd crush rule dump
Thank you,
Dominic L. Hilsbos, MBA
Director - Information Technology
Perform Air International, Inc.
DHilsbos(a)PerformAir.com
www.PerformAir.com
-----Original Message-----
From: Marcel Kuiper [mailto:ceph@mknet.nl]
Sent: Tuesday, July 21, 2020 9:38 AM
To: ceph-users(a)ceph.io
Subject: [ceph-users] Re: osd out vs crush reweight]
Hi Dominic,
This cluster is running 14.2.8 (nautilus) There's 172 osds divided
over 19 nodes.
There are currently 10 pools.
All pools have 3 replica's of data
There are 3968 PG's (the cluster is not yet fully in use. The number
of PGs is expected to grow)
Marcel
Marcel;
Short answer; yes, it might be expected behavior.
PG placement is highly dependent on the cluster layout, and CRUSH
rules.
So... Some clarifying questions.
What version of Ceph are you running?
How many nodes do you have?
How many pools do you have, and what are their failure domains?
Thank you,
Dominic L. Hilsbos, MBA
Director - Information Technology
Perform Air International, Inc.
DHilsbos(a)PerformAir.com
www.PerformAir.com
-----Original Message-----
From: Marcel Kuiper [mailto:ceph@mknet.nl]
Sent: Tuesday, July 21, 2020 6:52 AM
To: ceph-users(a)ceph.io
Subject: [ceph-users] osd out vs crush reweight
Hi list,
I ran a test with marking an osd out versus setting its crush weight
to 0.
I compared to what osds pages were send. The crush map has 3 rooms.
This is what happened.
On ceph osd out 111 (first room; this node has osds 108 - 116) pg's
were send to the following osds
NR PG's OSD
2 1
1 4
1 5
1 6
1 7
2 8
1 31
1 34
1 35
1 56
2 57
1 58
1 61
1 83
1 84
1 88
1 99
1 100
2 107
1 114
2 117
1 118
1 119
1 121
All PG's were send to osds on other nodes in the same room, except
for 1 PG on osd 114. I think this works as expected
Now I marked the osd in and wait until all stabilized. Then I set
the crush weight to 0. ceph osd crush reweight osd.111 0. I thought
this lowers the crush weight of the node so even less chances that
PG's end up on an osd of the same node. However the result are
NR PG's OSD
1 61
1 83
1 86
3 108
4 109
5 110
2 112
5 113
7 114
5 115
2 116
except for 3 PG's all other PG's ended up on an osd belonging to the
same node :-O. Is this expected behaviour? Can someone explain?? This
is on nautilus 14.2.8.
Thanks
Marcel
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