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Forum Discussion
Single iSCSI taret & 2 initiators...
I have a ReadyNAS 2100 in operation that has the following configuration...
1 x SMB share mounted on a SBS2K8 box
1 x iSCSI Target with a single 2TB LUN which has Access Control Enabled
The initiators are
1 Mac OS X 10.5.8 Server
1 Mac OS X 10.6.8 Server
They both mount the lun fine but the 10.6.8 server can't write to it.
I don't have CHAP authentication enabled.
Using the GlobsaSAN initiator these are the Settings...
- Error Detection: Header Only
- ISCSI Options: Always send "SessionType" when connecting is checked.
Always send "AuthMethod" when connecting is NOT checked.
- Connection is Persistent.
These settings are the same on both Mac Servers.
ReadyNAS Settings...
Availability: Enabled
LUN: 0
Access Control: enabled
Initiator IQNs:
naa.xxx
naa.xxx
(Where xxx is the full lowercase alpha-numercial string from the GlobalSAN control panel on each Mac Server)
Any ideas?
I am doing this so I can have both server backup to different folders on the sam LUN rather than having to manage seperate LUNS and volumes I can more esily migrate data or expand the LUN as required.
Cheers
1 x SMB share mounted on a SBS2K8 box
1 x iSCSI Target with a single 2TB LUN which has Access Control Enabled
The initiators are
1 Mac OS X 10.5.8 Server
1 Mac OS X 10.6.8 Server
They both mount the lun fine but the 10.6.8 server can't write to it.
I don't have CHAP authentication enabled.
Using the GlobsaSAN initiator these are the Settings...
- Error Detection: Header Only
- ISCSI Options: Always send "SessionType" when connecting is checked.
Always send "AuthMethod" when connecting is NOT checked.
- Connection is Persistent.
These settings are the same on both Mac Servers.
ReadyNAS Settings...
Availability: Enabled
LUN: 0
Access Control: enabled
Initiator IQNs:
naa.xxx
naa.xxx
(Where xxx is the full lowercase alpha-numercial string from the GlobalSAN control panel on each Mac Server)
Any ideas?
I am doing this so I can have both server backup to different folders on the sam LUN rather than having to manage seperate LUNS and volumes I can more esily migrate data or expand the LUN as required.
Cheers
6 Replies
Replies have been turned off for this discussion
- the simple answer is you can't do that. Iscsi does not provide for multiple simultanious access by 2 different initiators.
- Hi TeknoJnky thanks for your reply, maybe I am misguided somewhat but could you elaborate for me?
Why does the box indicate it can by allowing you to specify the initiator IQN?
iSCSI in my understanding and according to wikipedia "iSCSI imposes no rules or restrictions on multiple computers sharing individual LUNs; it leaves shared access to a single underlying filesystem as a task for the operating system."
So unless I am misunderstood or using the terminology incorrectly?
Many Thanks in advance "iSCSI imposes no rules or restrictions on multiple computers sharing individual LUNs; it leaves shared access to a single underlying filesystem as a task for the operating system."
That is precisely your problem - OS X provides no control of how the 2 initiators write to the LUN and so data corruption is highly possibly - probable even.
Consider an external HDD with firewire interface which often come with 2 ports to enable daisy-chaining. You could simultaneously connect the drive to 2 separate macs such that both use the disk and there would be no protection from both macs writing to the same location. That's what you have with one LUN and 2 initiators
Applications such as VMWare have controls built-in to deal with this scenario. There are also specialised File Systems designed to support this, but not easily supported on Mac
Networking protocols such as CIFS and AFP are specifically designed to enable simultaneous access to shared storage - iSCSI is not
Note: The developers of the initiator you are using also provide software that supports what you are trying to do - but it is substantially more expensive
http://www.studionetworksolutions.com/p ... l.php?pi=8- Aha must be why then I discovered this during a little testing....
SRV2 accesses and changes a file it locks it out to SRV1 becuase it doesnt know about the change, reformating the volume allows both to write simaltaneously but again problems arise.
SOOOoo given the backup software (crashplan) writes off to a VTL I'm going to remove the ISCSI volumes and create a guest AFP mount where they can both write their backups to simultaneously.
When I decommission one the Mac serves I will revert to iSCSI again as I find it more flexible/reliable and faster.
So theres my learning curve for the week iSCSI and multiple OSX (at least) initiators is a No No.
Thanks everyone for input and replies. - If you need to share data that is on an iscsi volume, you should mount the iscsi volume with a single server, then share the files out on that server via whatever protocol (cifs/nfs/atalk, etc).
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