iSCSI on ZFS

[Tekkie]

From reading the wiki on iSCSI I believe the only way of having iSCSI backed by RAIDZ storage, is to create a file extent and expose that as a drive to the world.

However I am finding it very difficult to know up front how much storage I will need on the iSCSI device.

Which brings me to my question, can I re-size an iSCSI extent once its been formatted by the connecting host?

 

[SoftDux-Rudi]

I don't know how this works on FreeNAS 8.x, but on FreeNAS 0.7.2 I simply setup a ZFS pool, then exported a portion of it via iSCSI - although I had to create a file in the ZFS pool, so I guess that adds some overhead.

Regarding the resize later on, it should be fine as long as your iSCSI client can handle it. I've increased iSCSI targets before, but not decreased, so I'm not sure if that's possible.

 

[Tekkie]

That sounds like the file extent method and what I've done, however there is also the Zvol option which just reserves a chunk of file space as a block device or not?

 

[Teqonix]

That sounds like the file extent method and what I've done, however there is also the Zvol option which just reserves a chunk of file space as a block device or not?

Yep, I just successfully configured the zvol option with RAIDZ1 on a ZFS pool today with the help of this thread: http://sourceforge.net/apps/phpbb/freenas/viewtopic.php?f=97&t=10545&p=51797&hilit=iSCSI+file+extent

Apparently this will be a feature implemented in the Web GUI in the next release, but until then - have fun with those config files! Also, be careful with the iSCSI webgui after you've implemented these changes. If you enable/disable the service or make any changes that affect /etc/local/istgt/istgt.conf; it will wipe out your changes.

 

[Tekkie]

Which means that its not an option as the istgt service requires a restart to commit change in the system. :(

PS. With FrreNAS8 you can create a Zvol and have that as a device extent mapped to a target in iSCSI, it works like a charm.

 

[Teqonix]

Which means that its not an option as the istgt service requires a restart to commit change in the system. :(

PS. With FrreNAS8 you can create a Zvol and have that as a device extent mapped to a target in iSCSI, it works like a charm.

Well, you can make it work - you just have to be careful about it. First, you shut down the service in the service control panel in the WebGUI, then you modify your istgt.conf file, and finally bring the service back online by manually running the /usr/bin/istgt binary. You basically can't ever touch the WebGUI again without rewriting your conf file, but it will work as a 'set it and forget it' method.

Of course all this is moot with the latest releases of FreeNAS 8 beta.

 

[brundle]

Where in the GUI can a zvol dataset be assigned to an Extent? I am on 8.0.1 beta3 and when I try to add an Extent the Disk Device selection list is still blank.

-b

 

[brundle]

I found where to do this. It does not exist in the left nav, only on the Active Volumes page in the body of the WebUI under the Storage category. There is a button for "Create ZFS Volume".

 

[Tiretz]

I created a 200Mb iSCSI file extent and connected to it with windows 7. I then increased the size to 500Gb in FreeNas. Without restarting FreeNas, Windows 7 Disk Management showed that the disk had increased (it took a minute or so), then I expanded the simple volume to fill the new size.