SPAM: [PATCH manager] fix #8193: ceph: pool set: keep min_size when changing size

SPAM: [PATCH manager] fix #8193: ceph: pool set: keep min_size when changing size

[Parker Wahle]

Since commit 76ed4900 ("fix #5010: ceph: pool set only changed
properties"), set_pool reads the pool's properties once, before
applying anything, and skips every requested setting that matches
them. Ceph resets min_size whenever size changes, which is why
set_pool applies size first. But a requested min_size equal to the
old one was still compared with the value from before that reset and
skipped, so Ceph's reset value stayed in place: for example, size=3
min_size=1 on a size 2 / min_size 1 pool left min_size at 2, and
size=3 min_size=3 on a size 4 / min_size 3 pool lowered it to 2.

This code change has PVE re-read the pool's properties after setting
the size, so the remaining settings are compared with the pool's
current values.

An LLM was used to isolate the cause of bug #8193 and draft a fix.
The fix was then tested against a reproducer on a live node and
found to work.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Parker Wahle <regulad@regulad.xyz>
---
 PVE/Ceph/Tools.pm | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/PVE/Ceph/Tools.pm b/PVE/Ceph/Tools.pm
index 94177709..ad5ba687 100644
--- a/PVE/Ceph/Tools.pm
+++ b/PVE/Ceph/Tools.pm
@@ -304,6 +304,8 @@ sub set_pool {
             print "$err";
         } else {
             delete $param->{$setting};
+            # Ceph resets min_size when size changes, so re-read before comparing the rest
+            $current_properties = get_pool_properties($pool, $rados) if $setting eq 'size';
         }
     }
 
-- 
2.56.0

Re: [PATCH manager] fix #8193: ceph: pool set: keep min_size when changing size

[Kefu Chai]

On Sun Oct 18, 2026 at 10:52 PM CEST, Parker Wahle wrote:
[snip]
> @@ -304,6 +304,8 @@ sub set_pool {
>              print "$err";
>          } else {
>              delete $param->{$setting};
> +            # Ceph resets min_size when size changes, so re-read before comparing the rest
> +            $current_properties = get_pool_properties($pool, $rados) if $setting eq 'size';
>          }
>      }

Thanks for tracking this down! I could reproduce it on a three-node
lab cluster running Ceph 21.1.2, with osd_pool_default_min_size = 2.
Without the patch, both of your examples lose the requested min_size:

- a 2/1 pool set to size=3 min_size=1 ends up with min_size 2
- a 4/3 pool set to size=3 min_size=3 ends up with min_size 2

With the patch, both keep the min_size that was asked for. I also
tried changing only the size, which still gives Ceph's default
min_size, and changing only min_size, which works as before. The pool
is only re-read when the size actually changes, which seems fine to
me.

Tested-by: Kefu Chai <k.chai@proxmox.com>
Reviewed-by: Kefu Chai <k.chai@proxmox.com>