[stgt] Late opening of the backing store

[Môshe van der Sterre]

On Thu, 19 Jan 2012 07:17:21 +0900, FUJITA Tomonori
<fujita.tomonori at lab.ntt.co.jp> wrote:
> On Wed, 18 Jan 2012 23:06:36 +0100
> **UNKNOWN CHARSET** <me at moshe.nl> wrote:
> 
>> For example, I want the ability to export all volumes in a LVM
>> volumegroup automatically, this can easily be done with a udev script
>> to
>> add the LUN. The same could be done for removing the volume, only stgt
>> prevents this by making LVM mark the device 'in use'. I would like a
>> option so stgt only 'uses' the device, if there is a connection that
>> _really_ uses the device.
> 
> Why you can't remove the device from tgt?

Manually, this is possible, however, the administration tool (LVM for
example) can't do this.
This is the issue I am trying to solve. udev triggers would work great
for this.

>> Is short this means stgt should defer the open() call on the backing
>> store until a connection is requested. Likewise, it should close() the
>> backing store when the last connection closes.
>> I am guessing such a feature does not yet exist (I couldn't find it),
> 
> tgt supports such feature for MMC logical units. But what tgt should
> return to initiators when the initiators try to access to devices that
> are not available?

I am not sure (I don't know that much about the internals of iSCSI), I
suppose the same thing as would happen now if a backing store is
unplugged/truncated while stgt has opened it?
Is this an error condition that is not possible with iSCSI?

Also, this would only happen when something has gone wrong, normally
stgt would (obviously) not have a logical unit configured that does 
not
exist.

Greetings,
Môshe van der Sterre

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