It executes the disk arbitration algorithm on the quorum disk to gain ownership. When the cluster service on the forming node starts, it first tries to bring online the physical device designated as quorum disk. Quorum disk is the first resource brought online when cluster service attempts to form a cluster. If the cluster is a shared disk cluster, one of the disks is designated as quorum disk by the cluster service. The volume is marked offline to prevent multiple nodes from having write access to the volumes simultaneously. Note that this is not the same as taking a cluster resource offline. When the first node in the cluster starts, the cluster disk driver first marks all LUNs (LUN: logical unit number, a unique identifier used on a SCSI bus to distinguish between devices that share the same bus) matching the Signatures key as offline volumes. When the computer is started, the Cluster Disk Driver (Clusdisk.sys) reads the following local registry key to obtain a list of the signatures of the shared disks under cluster management: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ClusDisk\Parameters \SignaturesĪfter the list is obtained, the cluster service attempts to scan all of the devices on the shared SCSI bus to find matching disk signatures. This scenario assumes that only one node is being turned on at a time: The following procedure describes how a server cluster starts and gains control of the shared disks. This command can either be a bus reset (for the entire bus) or, using the storport drivers a targeted reset for a particular device on the bus. Reset: This command breaks the reservation on a target device.
Release: This command is issued by the owning host bus adapter when a disk resource is taken offline it frees a SCSI device for another host bus adapter to reserve. A device that is reserved refuses all commands from all other host bus adapters except the one that initially reserved it, the initiator. Reserve: This command is issued by a host bus adapter to obtain or maintain ownership of a SCSI device.
The following list of commands is the additional SCSI protocol features that will be used when disks are in a clustered environment.
This does not mean that all disks will be of type SCSI, specifying the hardware interface known as SCSI, but rather that the storage unit must be able to properly interpret and process the SCSI protocol and commands.
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