Re: [Xen-devel] Handling iSCSI block devices (Was: Driver domains and device handling)

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Roger Pau Monne writes ("Re: Handling iSCSI block devices (Was: Driver domains 
and device handling)"):
> On 14/12/12 19:26, Ian Jackson wrote:
> > Roger Pau Monne writes ("Re: Handling iSCSI block devices (Was: Driver 
> > domains and device handling)"):
> >>  * remove: called to disconnect the device. Xenstore backend entries
> >> exists, and backend state is 6 (XenbusStateClosed).
> > 
> > I assume we need an unprepare here too.
> 
> I've also thought that, but the reason for prepare to exist is to reduce
> the time that the "add" operation takes, thus reducing the blackout
> phase during migration.

The unprepare operation might also be slow.  (Of course we believe in
crash-only software but the storage provider might not...)

> There's no such problem in the remove phase, but I guess we need an
> unprepare in case there's a failure between the prepare and add
> operations, and we wish to give the hotplug script an opportunity to
> unwind whatever the prepare operation has done.
> 
Yes.

Ian.

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