The DNS-323 doesn't offer any kind of faculty to do this.
NDAS devices, however, do to a certain extent. Through personal experience, however, I wouldn't use one of them under a wireless network.
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If you were running Linux of some kind and *if* D-Link gets NFS working correctly in 1.09 or later, you would be able to mount any of your 323s in a folder(s) of your choosing.
AFAIK, if you were using Windows Server 2003 or higher, you could deploy DFS and achieve one source of network shares from multiple devices, of which you could mount into one drive letter on WinXP.
As your post in the other forum indicates, iSCSI would also be an option, but you're never going to see that on the DNS-323. Keep in mind, the 323 only has 64MB of ram in it to run the OS and all of the utilities it comes with. D-Link offers
this on the high-end and
this on the entry level with the features you're looking for.
You're requesting an enterprise-class feature in a device that is destined for Home/SoHo. With 6 NASes it's probably time to "grow up" your storage solution and have a talk with a Tier 1 provider about inexpensive storage servers. For example, a Dell PowerVault NF500 running Windows Storage Server 2003 R2 (64-bit) with 6x 1TB SATA Hot Plug drives costs around $6,000. It's expandable with up to three MD1000 disk array enclosures for a total of 52 drives of capacity if you need it. Compare that to an EqualLogic or EMC SAN and you'll see the
huge cost savings of an entry-level enterprise storage server. PLUS you'll get the features you're looking for and get a huge speed boost.