Microsoft's mobile Vista will encourage notebook users to change to hybrid hard drives, which combine spinning disk and flash memory, according to a Microsoft requirements' document.

"Hybrid disk drives or systems that implement a hybrid disk drive must meet the requirements outlined here. This requirement will go into effect for premium mobile systems in June 1 2007," says the document. The requirement is: "A minimum of 50-MB NV Cache must be implemented in the H-HDD and exposed to Windows."

Both Samsung and Seagate are developing such hybrid drives. The idea behind them is that the notebook's battery life can be extended as the disk is spun up only when data in the cache needs refreshing or writing to the hard drive.

Another benefit is that system boot time can be significantly speeded up.

The Microsoft document, available by zip archive download states that: "Specific information is available in the white paper titled "Hybrid Hard Disk Support in Windows Vista." The white paper can be obtained by sending e-mail to [email protected]"

The document also notes changes to parallel SCSI support for a Windows Server failover cluster: "The way in which storage is managed on a Windows Server failover cluster is radically evolving. Fibre Channel, iSCSI, and SAS storage must support the new SCSI-3 persistent reservation commands to work correctly with failover clustering because the legacy reserve/release/reset mechanism is no longer used. Parallel-SCSI is no longer a supported storage type for shared failover cluster storage. This section outlines the set of requirements for using storage for failover clustering."