openstack-manuals/doc/admin-guide/source/ts-eql-volume-size.rst

Addressing discrepancies in reported volume sizes for EqualLogic storage

Problem

There is a discrepancy between both the actual volume size in EqualLogic (EQL) storage and the image size in the Image service, with what is reported to OpenStack database. This could lead to confusion if a user is creating volumes from an image that was uploaded from an EQL volume (through the Image service). The image size is slightly larger than the target volume size; this is because EQL size reporting accounts for additional storage used by EQL for internal volume metadata.

To reproduce the issue follow the steps in the following procedure.

This procedure assumes that the EQL array is provisioned, and that appropriate configuration settings have been included in /etc/cinder/cinder.conf to connect to the EQL array.

Create a new volume. Note the ID and size of the volume. In the following example, the ID and size are 74cf9c04-4543-47ae-a937-a9b7c6c921e7 and 1, respectively:

$ cinder create --display-name volume1 1

+-----------------------+-------------------------------------------+
|   Property            |   Value                                   |
+-----------------------+-------------------------------------------+
|   attachments         |   []                                      |
|   availability zone   |   nova                                    |
|   bootable            |   false                                   |
|   created_at          |   2014-03-21T18:31:54.248775              |
|   display_description |   None                                    |
|   display_name        |   volume1                                 |
|   id                  |   74cf9c04-4543-47ae-a937-a9b7c6c921e7    |
|   metadata            |   {}                                      |
|   size                |   1                                       |
|   snapshot_id         |   None                                    |
|   source volid        |   None                                    |
|   status              |   creating                                |
|   volume type         |   None                                    |
+-----------------------+-------------------------------------------+

Verify the volume size on the EQL array by using its command-line interface.

The actual size (VolReserve) is 1.01 GB. The EQL Group Manager should also report a volume size of 1.01 GB:

eql> volume select volume-74cf9c04-4543-47ae-a937-a9b7c6c921e7
eql (volume_volume-74cf9c04-4543-47ae-a937-a9b7c6c921e7)> show
_______________________________ Volume Information ________________________________
Name: volume-74cf9c04-4543-47ae-a937-a9b7c6c921e7
Size: 1GB
VolReserve: 1.01GB
VolReservelnUse: 0MB
ReplReservelnUse: 0MB
iSCSI Alias: volume-74cf9c04-4543-47ae-a937-a9b7c6c921e7
iSCSI Name: iqn.2001-05.com.equallogic:0-8a0906-19f91850c-067000000b4532cl-volume-74cf9c04-4543-47ae-a937-a9b7c6c921e7
ActualMembers: 1
Snap-Warn: 10%
Snap-Depletion: delete-oldest
Description:
Snap-Reserve: 100%
Snap-Reserve-Avail: 100% (1.01GB)
Permission: read-write
DesiredStatus: online
Status: online
Connections: O
Snapshots: O
Bind:
Type: not-replicated
ReplicationReserveSpace: 0MB

Create a new image from this volume:

$ cinder upload-to-image --disk-format raw \
  --container-format bare volume1 image_from_volume1

+---------------------+---------------------------------------+
|       Property      |                 Value                 |
+---------------------+---------------------------------------+
|   container_format  |                  bare                 |
|     disk_format     |                  raw                  |
| display_description |                  None                 |
|          id         | 74cf9c04-4543-47ae-a937-a9b7c6c921e7  |
|       image_id      | 3020a21d-ba37-4495-8899-07fc201161b9  |
|      image_name     |          image_from_volume1           |
|         size        |                  1                    |
|        status       |              uploading                |
|      updated_at     |      2014-03-21T18:31:55.000000       |
|     volume_type     |                 None                  |
+---------------------+---------------------------------------+

When you uploaded the volume in the previous step, the Image service reported the volume's size as 1 (GB). However, when using glance image-list to list the image, the displayed size is 1085276160 bytes, or roughly 1.01 GB:

Name	Disk Format	Container Format	Size	Status
image_from_volume1	raw	bare	1085276160	active

Create a new volume using the previous image (image_id 3020a21d-ba37-4495 -8899-07fc201161b9 in this example) as the source. Set the target volume size to 1 GB; this is the size reported by the cinder tool when you uploaded the volume to the Image service:

$ cinder create --display-name volume2 \
  --image-id 3020a21d-ba37-4495-8899-07fc201161b9 1
ERROR: Invalid input received: Size of specified image 2 is larger
than volume size 1. (HTTP 400) (Request-ID: req-4b9369c0-dec5-4e16-a114-c0cdl6bSd210)

The attempt to create a new volume based on the size reported by the cinder tool will then fail.

Solution

To work around this problem, increase the target size of the new image to the next whole number. In the problem example, you created a 1 GB volume to be used as volume-backed image, so a new volume using this volume-backed image should use a size of 2 GB:

$ cinder create --display-name volume2 \
  --image-id 3020a21d-ba37-4495-8899-07fc201161b9 1

+---------------------+--------------------------------------+
|       Property      |                Value                 |
+---------------------+--------------------------------------+
|     attachments     |                  []                  |
|  availability_zone  |                 nova                 |
|      bootable       |                false                 |
|     created_at      |      2014-03-21T19:25:31.564482      |
| display_description |               None                   |
|    display_name     |             volume2                  |
|         id          | 64e8eb18-d23f-437b-bcac-b3S2afa6843a |
|      image_id       | 3020a21d-ba37-4495-8899-07fc20116lb9 |
|      metadata       |                  []                  |
|        size         |                  2                   |
|    snapshot_id      |                 None                 |
|    source_volid     |                 None                 |
|       status        |               creating               |
|    volume_type      |                 None                 |
+---------------------+--------------------------------------+

Note

The dashboard suggests a suitable size when you create a new volume based on a volume-backed image.

You can then check this new volume into the EQL array:

eql> volume select volume-64e8eb18-d23f-437b-bcac-b352afa6843a
eql (volume_volume-61e8eb18-d23f-437b-bcac-b352afa6843a)> show
______________________________ Volume Information _______________________________
Name: volume-64e8eb18-d23f-437b-bcac-b352afa6843a
Size: 2GB
VolReserve: 2.01GB
VolReserveInUse: 1.01GB
ReplReserveInUse: 0MB
iSCSI Alias: volume-64e8eb18-d23f-437b-bcac-b352afa6843a
iSCSI Name: iqn.2001-05.com.equallogic:0-8a0906-e3091850e-eae000000b7S32cl-volume-64e8eb18-d23f-437b-bcac-b3S2afa6Bl3a
ActualMembers: 1
Snap-Warn: 10%
Snap-Depletion: delete-oldest
Description:
Snap-Reserve: 100%
Snap-Reserve-Avail: 100% (2GB)
Permission: read-write
DesiredStatus: online
Status: online
Connections: 1
Snapshots: O
Bind:
Type: not-replicated
ReplicationReserveSpace: 0MB