[libvirt] [PATCH v2] storage: vz storage pool support

Olga Krishtal okrishtal at virtuozzo.com
Thu Dec 8 16:39:27 UTC 2016

Hi all,  I see here a lot of discussions and explanations about 
virtuozzo storage. So, I will just add some information.
Initially I have planned, that admin or user has properly configured 
vstorage somewhere over the
network. (It can be done via DNS records or zeroconf.) At the host where 
pool will be stored
user/admin do cluster discovery and authorization. As Maxim has 
mentioned before - vstorage
does not use the concept of users and groups, providing specific users 
and groups with access to specific parts of a cluster.
So, anyone authorized to access a cluster can access all its data. 
However, you can use additional parameters
during mounting to define mount owner usr name, group name and acecss 
mode (so, you can mount cluster as read-only)
This means that performing chown/chmod and etc - will have same effect 
as in nfs case.
Of course to perform this operations you need vstorage-client to be 
installed on the host.

On 08/12/16 16:47, Maxim Nestratov wrote:
> 08-Dec-16 15:17, John Ferlan пишет:
>> On 12/08/2016 04:19 AM, Maxim Nestratov wrote:
>>> 08-Dec-16 02:22, John Ferlan пишет:
>>>> [...]
>>>>>> I see what you mean; however, IMO vstorage should be separate. Maybe
>>>>>> there's another opinion out there, but since you're requiring
>>>>>> "something" else to be installed in order to get the WITH_VSTORAGE
>>>>>> to be
>>>>>> set to 1, then a separate file is in order.
>>>>>> Not sure they're comparable, but zfs has its own. Having separated
>>>>>> vstorage reduces the chance that some day some incompatible logic is
>>>>>> added/altered in the *fs.c (or vice versa).
>>>>> Ok. I will try.
>>>>>> I think you should consider the *_fs.c code to be the "default" of
>>>>>> sorts. That is default file/dir structure with netfs added in. The
>>>>>> vstorage may just be some file system, but it's not something 
>>>>>> (yet) on
>>>>>> "every" distribution.
>>>>> I did not understand actually, what you mean  "be the "default" of
>>>>> sorts."
>>>>> As I have understood - what I need to do is to create 
>>>>> backend_vstorage.c
>>>>> with all create/delete/* functionality.
>>>> Sorry - I was trying to think of a better way to explain... The 
>>>> 'fs' and
>>>> 'nfs' pool are default of sorts because one can "ls" (on 
>>>> UNIX/Linux) or
>>>> "dir" (on Windows) and get a list of files.
>>>> "ls" and "dir" are inherent to the OS, while in this case vstorage
>>>> commands are installed separately.
>>> Once you mounted your vstorage cluster to a local filesystem you can
>>> also "ls" it. Thus, I can't see much difference from nfs here.
>> So if it's more like NFS, then how does one ensure that the local userid
>> X is the same as the remote userid X? NFS has a root-squashing concept
>> that results in numerous shall we say "interesting" issues.
> Vstorage doesn't have users concept. Authentication is made by a 
> password per node just once.
> If authentication passes, a key is stored in 
> /etc/vstorage/clusters/CLUSTER_NAME/auth_digest.key
> Then, permissions are set to a mount point during mounting with -u 
> USER -g GROUP -m  MODE options
> provided to vstorage-mount command.
>> Check out the virFileOpen*, virDirCreate, and virFileRemove...
>> Also what about viFileIsShareFSType? And security_selinux.c code for
>> NFS? If you use cscope, just search on NFS.
>> In the virStorageBackendVzStart, I see:
>>     VSTORAGE_MOUNT -c $pool.source.name $pool.target.path
> This call certainly lacks user/group/mode parameters and should be 
> fixed in the next series.
Do you mean fix the default behavior for non-root users?

>> where VSTORAGE_MOUNT is a build (configure.ac) definition that is the
>> "Location or name of vstorage-mount program" which would only be set if
>> the proper package was installed.
>> In the virStorageBackendVzfindPoolSources, I see:
>>     VSTORAGE discover
>> which I assume generates some list of remote "services" (for lack of a
>> better term) which can be used as/for pool.source.name in order to be
>> well mounted by the VSTORAGE_MOUNT program.
>> Compare that to NFS, which uses mount which is included in well every
>> distro I can think of. That's a big difference. Also let's face it, NFS
>> has been the essential de facto goto tool to access remote storage for a
>> long time. Personally, I'd rather see the NFS code split out of the
>> *_fs.c backend, but I don't have the desire/time to do it - so it stays
>> as is.
> To sum this up, you still think that copy and paste isn't a problem 
> here and will create more value than do any harm, right?
> Maxim
> [snip]

Best regards,

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