Blurring the line between NAS and SAN
But it is still true that SANs and NAS are blurring. For example, it would be feasible to build a dedicated storage network on Ethernet, with storage capacity provided by NAS boxes. Would this be a SAN? In some respects it would, but its reliance on file-based access might suggest otherwise.
Similarly, file servers sold by Network Appliance attach to Ethernet LANs but also use SAN technology for backup. They use Fibre Channel disk drives internally and can be inter-linked, so that several NAS boxes can share a single tape library.
Gale said that it is a question of what you are trying to achieve. 'We use Fibre Channel on the back end Ã, it's a good way of connecting storage,' he argued. 'But it's not good at multihost connectivity. Are all hosts going to share the same volume? If so, who's going to write the file system?'
His view is that because almost every system supports NFS or one of a handful of other file-server protocols, this is the best way to serve and share files. The alternative would be to have the same file system on every server, allowing them all to share storage devices at the more efficient block level.
Several developments are under way in this area, including the directly addressed file system (Dafs), which will also allow applications to access memory without going through the operating system.
There are also concepts that extend beyond both SANs and NAS, such as the creation of a storage utility. This is an architecture where all management and design tasks are hidden as much as possible, so it delivers content on demand without the need to worry about where it is physically stored or the identity of the storage supplier.
This will demand much more sophisticated storage management software than is available today, however, to build storage utilities, make up for the skills shortage that exists as data volumes grow and counteract the growing dearth of experienced staff.
'Human resource issues are driving backup, storage consolidation, storage resource management and virtualisation,' said Tom Clark, director of technical marketing at Fibre Channel switch developer Vixel. 'If I had enough slaves to do it, I would have everyone doing everything by hand. The pressure is to reduce cost and exposure to risk, and with administrative talent in such short supply it's an amazing driver.'
Wayne Rickard, chief technology officer of Gadzoox, who was recently made the chairman of the Storage Networking Industry Association's (SNIA) technical council, agrees. 'We recognise as an industry that there is a pressing need for management tools to be improved. We hear IT managers saying that it would be nice to run them on Ethernet because they know how to manage that. They say that with server-attached storage there was nothing to manage. Now IT managers need to be able to take blocks of storage and link them in an interesting way to their servers, making sure the switches don't become new problems.'
The difficulty for users is that it will all cost money, according to IDC storage analyst Claus Egge. 'Users don't appreciate how much money they will have to stump up for new storage management solutions,' he warned. 'But the development money has to come from somewhere, and considering the shortage of storage managers, it's not unreasonable.'
