Why was the iSCSI datastore discontinued?

Development
1

I am using iSCSI datastore from the beginning. And I am asking why it was pulled out of OpenNebula core?

I understand that the iSCSI solutions may not scale well with thousands of VMs.
We are using OpenNebula as great virtualization management console. It is great for smaller cloud usage. Mainly we are using it for easy single VM deployment in small development group. I like the simplicity of OpenNebula deployment.

I do not like shared LVM solution where all hosts has full access to whole shared disk storage and any badly behaving or bad synced host could overwrite any part of storage. I think that iSCSI storage, where only iSCSI target has full control over all storage and each host get access only to particular device is best for our use case.

But new addon-iscsi is now totally unsupported, especially with 4.14 release. It does not support snapshots and it has several critical bugs. Even more, it was stripped from base very poorly, there are many iscsi related functions left in core.

I have made many fixes and now I am working on publishing it. I have already made some pull requests, but still without any reaction.

I am now thinking if it is worth making effort to bring it again well supported.

What is your opinion?

2

I have to mention that I am using iSCSI Enteprise Target (iet) and I have no stability isues. I have written tgtadmin script as iet wrapper.

3

Hi Michael,

first of all thanks for your contribution!

We are not maintaining this plugin up-to-date, precisely because of what you say: after a while we figured that this didn’t scale and that we would rather focus our efforts on other backends. However, we also thought that some people would be interested in it, that’s why instead of removing it entirely we moved it to an addon.

An addon requires someone from the community willing to spend some time in keeping it up to date. It usually doesn’t take that much time, maybe couple of day’s work after each release (~3 o 4 months). Unfortunately this addon fell into the category of those where no maintainer stepped up.

I am more than willing to transfer the leadership of this addon to you if you want. From the core team we will not pursue the development of any addon actively, but we will do our best to make the life easier to the maintainers of the addons.

In any case I have merged your PRs, they look great, although I haven’t tested them, the code and the changes make a lot of sense.

I would like to kindly ask you to send one more PR: updating the compatibility version of the README.md: https://github.com/OpenNebula/addon-iscsi#compatibility :slight_smile:

I honestly think this kind of effort you’re putting in does make a lot of sense, and I really hope people will get involved and use this add-on. I understand many people might be discouraged by the current compatibility notice…

By the way, on an unrelated note, we have added a new iSCSI datastore for OpenNebula 5.0: https://github.com/OpenNebula/docs/blob/master/source/administration/storage/iscsi_ds.rst
Note that the approach is totally different than with this addon. This relies on an external iSCSI server, and the admin registers the already created iSCSI targets. Whereas in this addon the iSCSI target is created by OpenNebula…

In any case, please let me know if you would like to take the leadership of this add-on, and thanks a lot for the contributions!

4

Hi Jaime,

I am using this addon and maintaining it for our usage. But I am using it with different iSCSI target than tgt. I have written wrapper script for tgtadmin simulating original functionality but translating commands to ietadm. So I think there should be someone testing it on original tgt instalation.

I have made README pull request. Now I am preparing and testing “snapshots” implementation.

I am also preparing fix for CDROM issue (it fails if same CDROM image is used more than one time on the same host), but it is not easy: https://github.com/OpenNebula/addon-iscsi/issues/12.

So may be I could be a maintainer, but I need someone else to do tests on real tgt.

Is there anybody using addon-iscsi with TGT and want this addon to be supported on newer OpenNebula?

1 Like