[TripleO Wallaby] - Multi-attach Volume showing different files
Hi Team, On TripleO Wallaby deployment, I have tried creating multi-attach type volume, which if I am attaching this volume to two VM, it is getting attached. After mounting the same in each VM, if I am creating the folders in one VM at the mount path, I am not seeing the same on the other VM at the mount path [image: image.png]
Ideally if the backend volume is same and if I am understanding the idea correctly, then the content should be same in both the location, as the back is same. Checking at horizon I also see that Volume is showing attached to both the VMs.
[image: image.png]
Document followed to create this: https://docs.openstack.org/cinder/latest/admin/volume-multiattach.html
Please advice
Hi Team, It worked if I redo the VM creation with creation one more volume of multi-attach type. Thanks once again for the same.
we can mark this thread as closed.
On Mon, Aug 29, 2022 at 11:18 AM Lokendra Rathour lokendrarathour@gmail.com wrote:
Hi Team, On TripleO Wallaby deployment, I have tried creating multi-attach type volume, which if I am attaching this volume to two VM, it is getting attached. After mounting the same in each VM, if I am creating the folders in one VM at the mount path, I am not seeing the same on the other VM at the mount path [image: image.png]
Ideally if the backend volume is same and if I am understanding the idea correctly, then the content should be same in both the location, as the back is same. Checking at horizon I also see that Volume is showing attached to both the VMs.
[image: image.png]
Document followed to create this: https://docs.openstack.org/cinder/latest/admin/volume-multiattach.html
Please advice
-- ~ Lokendra skype: lokendrarathour
On Mon, Aug 29, 2022 at 8:54 AM Lokendra Rathour lokendrarathour@gmail.com wrote:
Hi Team, It worked if I redo the VM creation with creation one more volume of multi-attach type. Thanks once again for the same.
we can mark this thread as closed.
On Mon, Aug 29, 2022 at 11:18 AM Lokendra Rathour < lokendrarathour@gmail.com> wrote:
Hi Team, On TripleO Wallaby deployment, I have tried creating multi-attach type volume, which if I am attaching this volume to two VM, it is getting attached. After mounting the same in each VM, if I am creating the folders in one VM at the mount path, I am not seeing the same on the other VM at the mount path [image: image.png]
Ideally if the backend volume is same and if I am understanding the idea correctly, then the content should be same in both the location, as the back is same.
Well, that's not quite how multiattach volumes are intended to work. The feature relies on your application and/or filesystem to support multiattach/cluster aware volumes. You can't just use a regular filesystem (ext4, etc.) and expect changes to the volume that are made from one attached vm to propagate to other vms attached to the same volume.
Alan
Checking at horizon I also see that Volume is showing attached to both the
VMs.
[image: image.png]
Document followed to create this: https://docs.openstack.org/cinder/latest/admin/volume-multiattach.html
Please advice
-- ~ Lokendra skype: lokendrarathour
-- ~ Lokendra skype: lokendrarathour
I'm afraid what you are trying is completely wrong. In case you need a shared file system then you should use a different technology like Manila.
Multiattach in cinder allows multiple VMS to access the same block device data but it does NEVER provide any mechanism to guarantee consistency at file system level. Popular filesystems such as xfs never protect concurrent IO from multiple machines and If you mount the filesystem on the shared disk by multiple vms and write on it concurrently then you'd end up with a corrupted filesystem.
Usually when you have multiattach-ed block devices then you need to implement a mechanism to prevent concurrent access (eg. Pacemaker)
On Tue, Aug 30, 2022 at 1:06 AM Lokendra Rathour lokendrarathour@gmail.com wrote:
Hi Team, It worked if I redo the VM creation with creation one more volume of multi-attach type. Thanks once again for the same.
we can mark this thread as closed.
On Mon, Aug 29, 2022 at 11:18 AM Lokendra Rathour < lokendrarathour@gmail.com> wrote:
Hi Team, On TripleO Wallaby deployment, I have tried creating multi-attach type volume, which if I am attaching this volume to two VM, it is getting attached. After mounting the same in each VM, if I am creating the folders in one VM at the mount path, I am not seeing the same on the other VM at the mount path [image: image.png]
Ideally if the backend volume is same and if I am understanding the idea correctly, then the content should be same in both the location, as the back is same. Checking at horizon I also see that Volume is showing attached to both the VMs.
[image: image.png]
Document followed to create this: https://docs.openstack.org/cinder/latest/admin/volume-multiattach.html
Please advice
-- ~ Lokendra skype: lokendrarathour
-- ~ Lokendra skype: lokendrarathour
Thank you for the clarification. Will check the approach suggested by you.
-Lokendra
On Mon, 29 Aug 2022, 21:53 Takashi Kajinami, tkajinam@redhat.com wrote:
I'm afraid what you are trying is completely wrong. In case you need a shared file system then you should use a different technology like Manila.
Multiattach in cinder allows multiple VMS to access the same block device data but it does NEVER provide any mechanism to guarantee consistency at file system level. Popular filesystems such as xfs never protect concurrent IO from multiple machines and If you mount the filesystem on the shared disk by multiple vms and write on it concurrently then you'd end up with a corrupted filesystem.
Usually when you have multiattach-ed block devices then you need to implement a mechanism to prevent concurrent access (eg. Pacemaker)
On Tue, Aug 30, 2022 at 1:06 AM Lokendra Rathour < lokendrarathour@gmail.com> wrote:
Hi Team, It worked if I redo the VM creation with creation one more volume of multi-attach type. Thanks once again for the same.
we can mark this thread as closed.
On Mon, Aug 29, 2022 at 11:18 AM Lokendra Rathour < lokendrarathour@gmail.com> wrote:
Hi Team, On TripleO Wallaby deployment, I have tried creating multi-attach type volume, which if I am attaching this volume to two VM, it is getting attached. After mounting the same in each VM, if I am creating the folders in one VM at the mount path, I am not seeing the same on the other VM at the mount path [image: image.png]
Ideally if the backend volume is same and if I am understanding the idea correctly, then the content should be same in both the location, as the back is same. Checking at horizon I also see that Volume is showing attached to both the VMs.
[image: image.png]
Document followed to create this: https://docs.openstack.org/cinder/latest/admin/volume-multiattach.html
Please advice
-- ~ Lokendra skype: lokendrarathour
-- ~ Lokendra skype: lokendrarathour
participants (3)
-
Alan Bishop
-
Lokendra Rathour
-
Takashi Kajinami