openstack
/
charm-glance
Code Issues Proposed changes

Remove rbd_store_chunk_size=8 reverting to default 

We have shipped rbd_store_chunk_size=8 in our glance configuration for a
very long time, this value was sometimes suggested in older upstream
documentation and has the effect of halving the number of rados objects
used to store glance images.

When using qcow2 images in ceph the created VM volume will have an
rbd_store_chunk_size=4 (the default) however in modern clouds when
images are in the raw format we will use copy-on-write cloning from the
image to the volume, which means all such VM volumes inherit
rbd_store_chunk_size=8 from the parent. This has negative performance
implications for working volumes as there are object-wide locks that now
cover twice as much data and a wider chunk of sequential disk storage
will hit the same OSD.

Any overhead benefit of using objects only double the size (and thus
half in number) is very likely long relegated to history given the
number of volumes we're likely to have in a cloud versus base images, so
there doesn't seem to be any benefit to this setting and outside of a
few glance documents this rbd option is not documented anywhere I can
find as a suggestion or with any evidence of an advantage of performance
improvement from storing images this way.

Remove rbd_store_chunk_size=8 from all configuration files so that it
reverts to the default of 4.

Existing images (and old or new dependent volumes of them) will maintain
the existing rbd_store_chunk_size=8 and continue to work correctly. New
images will be created with the new rbd_store_chunk_size=4.

Change-Id: I5f6801c418430bbdcda53b94fcd51ed2fc230b68
This commit is contained in:
Trent Lloyd 2020-07-07 14:13:29 +08:00
parent 160ba6e252
commit e553d095d6
7 changed files with 0 additions and 7 deletions
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1
templates/icehouse/glance-api.conf
View File

@ -68,7 +68,6 @@ swift_enable_snet = False
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
delayed_delete = False

1
templates/juno/glance-api.conf
View File

@ -71,7 +71,6 @@ swift_enable_snet = False
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
delayed_delete = False

1
templates/kilo/glance-api.conf
View File

@ -77,7 +77,6 @@ swift_enable_snet = False
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
[image_format]

1
templates/mitaka/glance-api.conf
View File

@ -69,7 +69,6 @@ swift_store_create_container_on_put = true
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
[image_format]

1
templates/ocata/glance-api.conf
View File

@ -73,7 +73,6 @@ swift_store_create_container_on_put = true
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
[image_format]

1
templates/queens/glance-api.conf
View File

@ -73,7 +73,6 @@ swift_store_create_container_on_put = true
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
[image_format]

1
templates/stein/glance-api.conf
View File

@ -69,7 +69,6 @@ swift_store_create_container_on_put = true
rbd_store_ceph_conf = /etc/ceph/ceph.conf
rbd_store_user = {{ rbd_user }}
rbd_store_pool = {{ rbd_pool }}
rbd_store_chunk_size = 8
{% endif -%}
[image_format]