[openstack-dev] [nova] Availability of device names for operations with volumes and BDM and other features.

Nikola Đipanov ndipanov at redhat.com
Thu Jun 11 09:25:53 UTC 2015

On 06/02/2015 01:39 PM, Alexandre Levine wrote:
> Thank you Nikola.
> We'll be adding the required tickets and will follow your reviews,
> however the person working primarily on this subject (Feodor Tersin) is
> out for his vacation for a couple of weeks so some of our responses
> might be delayed until then. Still we'll try to do whatever can be done
> without him at the time being.
> Best regards,
>   Alex Levine

Hi guys - I have some fixes posted [1]

As said below - reviews, and especially testing would be greatly
appreciated (even before they are merged).

NB: there is still some work needed to fix [2] on your side even if we
decide that my proposed approach is something we want to go with. See
comments on the bug and the related proposed patch for more information.


[2] https://bugs.launchpad.net/nova/+bug/1370250

> On 5/29/15 11:32 PM, Nikola Đipanov wrote:
>> On 05/29/2015 12:55 AM, Feodor Tersin wrote:
>>> Nicola, i would add some words to Alexandre repsonse.
>>> We (standalone ec2api project guys) have filed some bugs (the main is
>>> [1]), but we don't know how to fix them since the way Nova's device
>>> names are moved on is unclear for us. Neither BP, nor wiki you've
>>> mentioned above don't explain what was happened with device names in
>>> images.
>>> Other bug which we filed by results of bdm v2 implementation [2] was
>>> resolved, but the fix returns only two devices (even if more than two
>>> volumes are defined in the image) instead of to write device names to
>>> the image and to return full bdm.
>>> I hope you will clarify this question (Alexandre referred to the patch
>>> with explicit elimination of device names for images).
>>> Also you mentioned that we can still use bdm v1. We do it now for
>>> instance launch, but we would like to switch to v2 to use new features
>>> like blank volumes which are provided by AWS as well. However v2 based
>>> launch has a suspicious feature which i asked about in ML [3], but no
>>> one answered me. It would be great if you clarify that question too.
>>> [1] https://bugs.launchpad.net/nova/+bug/1370177
>>> [2] https://bugs.launchpad.net/nova/+bug/1370265
>>> [3]
>>> http://lists.openstack.org/pipermail/openstack-dev/2015-May/063769.html
>> Hey Feodor and Alexandre - Thanks for the detailed information!
>> I have already commented on some of the bugs above and provided a small
>> patch that I think fixes one bit of it. As described on the bug - device
>> names might be a bit trickier, but I hope to have something posted next
>> week.
>> Help with testing (while patches are in review) would be hugely
>> appreciated!
>> On 05/28/2015 02:24 PM, Alexandre Levine wrote:
>>> 1. RunInstance. Change parameters of devices during instance booting
>>> from image. In Grizzly it worked so we could specify changed BDM in
>>> parameters, it overwrote in nova DB the one coming from image and then
>>> started the instance with new parameters. The only key for addressing
>>> devices in this use case is the very device name. And now we don't have
>>> it for the volumes in BDM coming from the image, because nova stopped
>>> putting this information into the image.
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_RunInstances.html
>>> 2. Devices names for Xen-backed instances to work fully. We should be
>>> able to specify required device names during initial instance creation,
>>> they should be stored into an image when the instance is shapshotted, we
>>> can fetch info and change parameters of such volume during subsequent
>>> operations, and the device names inside the instance should be named
>>> exactly.
>>> 3. DescribeInstances and DescribeInstanceAttributes to return BDM with
>>> device names ideally corresponding to actual device naming in instance.
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeInstances.html
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeInstanceAttribute.html
>>> 4. DescribeImages and DescribeImageAttributes to return BDM with device
>>> names ideally corresponding to the ones in instance before snapshotting.
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeImages.html
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeImageAttribute.html
>> I think all of the above is pretty much covered by
>> https://bugs.launchpad.net/nova/+bug/1370177
>>> 5. AttachVolume with the specified device name.
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_AttachVolume.html
>>> 6. ModifyInstanceAttribute with BDM as parameter.
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_ModifyInstanceAttribute.html
>>> 7. ModifyImageAttribute with BDM as parameter.
>> http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_ModifyImageAttribute.html
>> I am not sure about these 3 cases - would it be possible to actually
>> report bugs for them as I don't think I have enough information this way.
>> N.
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