Cooking with NDAS: trying out the Iocell NetDisk
I like my food, which won’t come as any surprise if you’ve closely examined the picture at the head of this column.
Never mind about my avoirdupois, though; this is one of my normal oblique opening gambits intended to introduce a serious point about network architectures.
It all started with Jonathan Bray’s review of the Iocell NetDisk 351UNE, a device costing a handsome £52 that performs a job which, at least superficially, you ought to be able to do for £22 last time I looked around the stalls at a computer fair.
The NetDisk is an unassuming plastic box that holds a SATA drive, the back of which contains connections for USB 2, eSATA and Ethernet cables.
It’s therefore difficult to distinguish between this device and those wobbly piles of add-on hard disk enclosures that you’ll see at computer fairs and clogging up eBay auctions. The difference is that if you’re going to make use of the Iocell sensibly, you first need to get your hands on the cookbook (see how I managed the segue?).
This is because the NetDisk 351 makes use of NDAS, which is a whole architecture for attaching a variety of PCs to a variety of hard disks in a variety of topologies, which is a bit like saying that a cookbook is about mixing up different ingredients – it’s sort of true, but glosses over all the important details you need to know.
Bad cookbooks are famous for having recipes that say things such as “first obtain a spatchcocked iguana”, while good cookbooks may offer exactly the same dish but go out of their way to tell you where to buy an iguana and how to spatchcock one. (Incidentally, my favourite example of this latter kind of cookbook is here.)
As regards the presentation of NDAS and all the different things that you can achieve with it – and which of them you should even attempt – then my protracted series of tests using four of these single-drive enclosures suggests that the potential pitfalls don’t lie in the software, nor in the concept itself, but elsewhere.
The idea behind NDAS is similar to the idea behind some of its larger-scale competitors such as CoRAID. All their inventors have decided that if you need to talk down a piece of network wire, there’s no law that says you must use TCP/IP to do so. TCP/IP was designed as a general-purpose transport protocol, which happens to be very useful for carrying the huge variety of data-types that are slung across the internet.
That doesn’t automatically make it ideal for the things that happen across the smallest possible network – a single cable plugged between two MDI-X autosense devices – nor across the usual sized home or small-business network that consists of some wire, perhaps a Wi-Fi section and typically nothing more exciting than the spare ports on the back of an internet router.
NDAS is delivered in two parts: inside the Iocell box there’s a chipset with some firmware in it, and then there’s a CD to put in your PC that installs NDAS software and a grab-bag of other utilities for backup and management, most of them branded by Iocell itself.
Most of its pages are in fact the same four diagrams with a dozen different language captions
To make NDAS work, you have to put a hard drive into the plastic case and run the PC installer to add a couple of programs, one of which has to be run to associate the key printed on the bottom of the NetDisk box with the software install for that specific host PC.
All of this is described in a slim but nicely designed pamphlet in the box, which looks excellent until you realise that most of its pages are in fact the same four diagrams with a dozen different language captions.
Up and running
Having got the first NetDisk box running, I thought I should investigate how it does what it does by poking around on the test machine.
Aside from the two utility programs (which could see the 351 straight away), there was very little to see – although there was a new protocol added to the Network Connection control panel – and I certainly couldn’t see any way to alter the IP address of the device, nor could I work out whether it was going to fill up my DHCP lease allocation, nor how to tell it what VLAN it should live in.
To cut to the chase, NDAS doesn’t operate in a space anywhere near your normal network traffic layers, but lives somewhere down around Layer 2, where MAC addresses identify individual chunks of hardware.
It’s presented as an additional protocol called LPX – for Light Packet Exchange – and it takes only a little bit of Googling to discover the originators of this protocol. NDAS (and hence LPX) are both the patented intellectual property of XiMeta, a firm that has been in the market with its version of this concept for half a decade or more.
The XiMeta website makes bold claims for the whole architecture, saying “the data process path and speed is just as durable and fast as a computer’s internal storage drive”, and there are other statements to the effect that this system doesn’t require a server to present shared documents over a network.
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