[pve-devel] [PATCHv2] Add support for multipath-backed direct attached storage

[Wolfgang Bumiller]

We're still unsure about the real use case. If you can add a device to a
list manually then it's also not much more work to add a raw device to a
VM via the commandline. In both cases you need to access the console,
and you typically don't add/remove/move disks around constantly, so it's
just a setup issue. So we're currently not convinced to include this by
default.

At the same time adding devices automatically instead seems like a
non-trivial task (and security critical).

Still, a note about the implementation: You might want to add a storage
name column to the list so that you can define more than just one such
storage. This would allow a more flexible permission management.
Also if you're already listing device names there's no real reason to
restrict it to multipath devices. But if you don't need more than this
it might be easier to just leave it the way it is, since there are no
promises this will get merged.

On Thu, Jun 30, 2016 at 01:21:27PM +0300, Dmitry Petuhov wrote:
> This patch series adds storage type "mpdirect". Before using it, multipath-tools
> package must be installed. After that, multipathd will create /dev/disk/by-id/wwn-0x*
> devices, which can be directly attached to VMs via GUI. Partitions are ignored.
> 
> I'm not skilled in UI programming, so there's no storage addition via UI. Just add
> 
> mpdirect: STORNAME
>         content images,rootdir
> 
> to storage.cfg.
> 
> Because of usage of multipath, this plugin is media-independent:
> it was tested with iSCSI, but should also work with FC and SAS/SCSI.
> 
> May need manual storage bus rescans to dynamically add new LUNs.
> 
> In 2nd version we use text file /etc/pve/multipath.list. File format:
> $wwn\s+\$name
> 
> $name must be in format vm-$N-disk-$M
> 
> Other storage-specific wwn-name mapping methods can be added later by using
> LunCmd/* modules.