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These notes are split into three parts;
a) How to set up a iSCSI target
b) Some thoughts on how to integrate iSCSI into DeviceKit-disks,
Palimpsest and the GNOME desktop
Keep in mind that a) and b) are merely my research notes used for
investigating iSCSI. All of this stuff is preliminary.
------------------------------------------------------------------------
iSCSI target bits (the machine exporting a device)
------------------------------------------------------------------------
This is using scsi-target-utils-0.0-4.20071227snap.fc9.x86_64
killall -9 tgtd
service tgtd restart
tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.2001-04.com.example:storage.disk2.amiens.sys1.xyz
tgtadm --lld iscsi --op new --mode logicalunit --tid 1 --lun 1 -b /dev/sdc
tgtadm --lld iscsi --op new --mode account --user davidz --password iscsi123
tgtadm --lld iscsi --op bind --mode account --tid 1 --user davidz
tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL
tgtadm --lld iscsi --op show --mode target
This exports the device /dev/sdc as an iSCSI target; will have to use
username 'davidz' and 'iscsi123' when initiating a connection. This
iSCSI target implementation doesn't seem capable of pass-through, e.g.
you can't share an optical drive and expect the initiator side to use
it for burning/dvd viewing.
There's also another iSCSI target implemetation in Livna, called
iscsitarget. See http://sourceforge.net/projects/iscsitarget/. This
one appeared to be able to export the cdrom drive (at least I could
mount the UDF file system); yet the initiator side didn't see it as a
cdrom drive. E.g. probably no pass-through support.
TODO: Need to find a good iSCSI target implementation.
------------------------------------------------------------------------
Teaching DeviceKit-disks / Palimpsest / GNOME about iSCSI devices
------------------------------------------------------------------------
First the 'why': there's a couple of reasons why iSCSI is interesting
to integrate with the desktop stack and disk management graphical
tools:
- It's generally a good idea to have graphical UI for OS
configuration bits in addition to configuration files and command
line tools. It's also not sufficient to just have UI tools
available at install time; people need to be able to tweak things
at run time as well.
- Both high-end laptops (e.g. Macbook Air, Lenovo X61, etc.) and
cheap sub-notebooks (e.g. Eee) doesn't come with optical
drives. Yet, users still need to be able to access storage media on
CD/DVD/Blu-Ray for both entertainment (e.g. watching DVD's) and
work (e.g. burning files to optical discs). It would be useful
to just use the optical drive from a desktop machine for this.
Now to the 'how' part. First of all any integration being done should
not render existing uses of iSCSI non-working and it shouldn't, as far
as possible, be a parallel configuration stack to what people are
currently using. The latter point means that if people use e.g.
iscsiadm(1) on the command line, the results of their changes should
appear in the UI as well.
------------------------------------------------------------------------
Changes needed on the initiator side:
------------------------------------------------------------------------
DeviceKit-disks changes:
- add 'iscsi' as valid value for drive-connection-interface
- and add new properties in the drive-iscsi-* namespace, e.g.
- name
- portal
- portal-port
- portal-group
- possibly information about current connection state
- may need to patch/fix the kernel to emit 'change' uevents
when this changes
- with this we can show notifications when there are
connection problems
- provide a way to enumerate iSCSI devices already setup; on
the org.freedesktop.DeviceKit.Disks interface add
- IScsiEnumerateEntries() that returns
{ s: name
s: portal
i: portal-port
i: portal-group
b: autostart
<possible more, including auth details> }
- IScsiAddEntry(), IScsiRemoveEntry(), IScsiConfigureEntry()
- to add, remove and configure iSCSI associations
- might need changes to iscsiadm(1) so we can pipe
the password instead of including it on the command line
- signal IScsiEntriesChanged()
- may need to watch the iscsiadm(1) config files to listen
to changes
- IScsiEntryStart(), IScsiEntryStop()
- to login resp. logout to an iSCSI device
libgdu / palimpsest changes:
- Like we do with Linux MD, make iSCSI drives implement the
GduActivableDrive interface. That way the user can start/stop
iSCSI drives. E.g. associated but non-connected iSCSI drives
should show up in the UI.
- When an iSCSI drive is selected, provide a GduSection with
widgets to change auth details etc. Similar to e.g.
GduSectionLinuxMd.
- Provide a way to create new iSCSI associations; probably just
an entry in the "File" menu in Palimpsest. Probably needs some
method on DeviceKit-disks to probe a portal for targets.
Nautilus / gvfs / desktop shell changes:
- With a gvfs volume monitor based on libgdu (I'm working on it!)
that supports un-activated GduActivatableDrive instances, all
iSCSI associations will show up in the file manager and one
can double click the entry to activate it. Once logged into
the iSCSI target, it just appears as a normal local device.
Meaning it's accessible to any application
- Ideally iSCSI targets that one can connect to would show up
in network:///. There's a couple of protocols available for
iSCSI discovery but none of them seems to support mDNS. Need
some research here.
- Desktop notifications when a iSCSI connection is broken; user
should be able to disconnect / disassociate from the iSCSI
device
- For end user UI, should integrate with the "Personal File Sharing"
capplet; Bastien wants to rename it to e.g. "Sharing" since it
will also do other things like swallow the screen sharing bits.
------------------------------------------------------------------------
Changes needed on the target side
------------------------------------------------------------------------
TODO: this is probably simple UI wise (e.g. have "Share this drive"
checkbox etc.) but need to figure out what iSCSI target implementation
to depend on.
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