Essentially a SAN is just another device to Microsoft OS. But, the current thinking is that the SAN volume(s) needs to be represented to the server via a virtualization technique. One virtualization engine I happen to like at present is DataCore Software, so I referred your question to them for a more explicit answer. Here's what they say:
"In Microsoft environments that are powered by DataCore, advanced virtualization nodes act as powerful brokers between the MS servers and the network storage pool, allowing virtual disks to be added, upgraded, replicated and reassigned without taking the hosts down. "The physical storage devices are first segregated from the MS servers to eliminate LUN ownership conflicts. The network of virtualization nodes takes over exclusive ownership of the devices by directly connecting to SCSI, ATA, EIDE and SSA arrays or by zoning Fibre Channel arrays for their private control. The central storage administrator then carves out arbitrarily sized virtual volumes from the physical drives and RAID devices, assigning specific properties to them, such as remote mirroring, and caching. This is done from an intuitive GUI with a global view of storage resources and servers (consumers)."The MS servers are separately zoned to the virtualization nodes. They see only selected virtual disks explicitly assigned to specific host ports using DataCore's secure binding. For clustered MS Servers, the same virtual volume may be defined as shared so two hosts can independently access it. Note that neither the SAN-connected MS servers nor the physical disks require any virtualization software to make this work.
"When the central storage administrator gets a request to give a server more capacity, he/she simply clicks, drags and drops an appropriate virtual volume and assigns it to a selected port on the needy host. Running Windows Disk Administrator on the MS Server reveals the additional capacity, which appears as a well-behaved new disk of the specified size. At that point, the server administrator can format the virtual disk and establish a file system just like an ordinary disk.
"Capacity may also be reassigned (and removable virtual devices defined) by simply disassociating the virtual disk from one MS server and assigning it to another. This is a very effective and dynamic way to deal with seasonal and unexpected demands."
Thanks for the question.
This was first published in March 2001