iSCSI for Apple, anyone?

Well, it seems like it's been a long, long time since we first came across a new storage connectivity protocol  called iSCSI. As many of you already know iSCSI works by encapsulating SCSI commands and transmitting them over any existing IP network, whatever its size.

iSCSI was going to make SANs fall within the reach of anyone with some iSCSI storage targets and more than one computer and everyone would live happily ever after. To be honest it seems that there has been a lot of interest in iSCSI where shared storage is concerned, anyone thinking of implementing a SAN would be mad not to consider it on its cost saving alone. In Windows and Linux environments you struggle to get an iSCSI based SAN not to work (given the appropriate sharing software is implemented) but in the Apple environment things seem sadly the opposite.

There's no shortage of iSCSI initiators available for Mac; Atto, Studio Network Solutions and Small Tree are the most obvious choices, but I've found performance and continuation of service a bit of an issue. 

For example, any of the above initiators may work with your iSCSI storage target of choice, lets say the excellent UD4116RM from United Digital for example. The 4116 is a 4 port iSCSI solution with multiple volume support, RAID levels from 0 - 60 and built in snapshot facility. It's performance on the Windows platform is impeccable, delivering around 120MBs per port all day long, but whilst performing the same tasks on our Apple kit things start to become quite sinister....

It's not a performance issue; you can quite happily get similar performance figures especially if you bump up the MTU rate to its 8000 max. The problem is whatever joy you feel as you watch the data fly back an forth from your storage target (I must point out this is not just an issue with UD storage targets, it is indeed almost universal) is very short lived as your Mac feels as if its simply had enough and nothing can wake it from its iSCSI induced catalepsy. Only a swift jab to the power button will revive it.

That said, you could quite happily send trickles of data to and from your iSCSI target, maybe by using it with Time Machine or something similar but open the floodgates at your own risk.

It probably goes without saying that if its serious I/O performance you are after on your Apple platform then stick to Fibre Channel or external PCIe (watch this space for more info). If you are just after some light usage secondary  or even near line storage for your Mac then you could consider iSCSI but what we have found is results do vary, whatever the manufacturer.

Feel free to contact us with your iSCSI success/horror stories, feedback is always appreciated.....