dannyo - there are multiple considerations, but if you look carefully at the cable, it is a PLAIN USB extension cable. It says "micro", but it really standard A male to standard A female.

First, the cable. If it is indeed micro-a, it will automatically put a stock n810 into host mode. If it doesn't, you need to run scripts (see the wiki or search to fora) to force it into host mode, or put it back into OTG/peripheral mode.

Second, the disk. If it uses something less than 200ma for the USB interface (part of the USB protocol is current requirements), it will work with just the micro to USB female cable. If it SAYS it uses more than that, you will need a powered hub in between. Note disks usually ask for maximum possible, so unless it is a battery powered case it will usually ask for much more. The 2nd generation iPod charged via firewire so works stock, but the newer models ask for "recharge battery" levels of power. Some flash drives and card adapters don't need hubs, others do.

Third, the disk needs to be formatted vanilla FAT (or ext2), and more importantly have a standard Windows/DOS Master boot record for partitioning.

So, if the n810 is in the host mode - via cable sense or scripts, and if the USB interface on the disk doesn't draw too much power OR you have a powered hub, and if the disk is normal format, it will appear in the file manager and even launch it if it isn't opened and you can access your files. I constantly use my micro to mini host mode with a mini b to female A with microSD keychain drives because it is faster than shuffling adapters into the miniSD slot.