Highly Available File Servers
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Q. Can I have an active/active file server?
A. The Windows 2000 resource kit contains a tool ClusTool that can be used to migrate file share settings from a single node to a cluster environment.
Q. Can FRS be used to replicate clustered file shares?
A. No, the file replication service (FRS) provided by Windows cannot be used to replicate a clustered file share. This means that clustered file shares cannot be the source or target for redundant links in a DFS tree. See the online documentation for DFS for more details.
Q. What file system types are supported in a cluster?
A. All partitions on clustered disks should be formatted with NTFS.
Q. Does client-side caching (offline folders) work with Server clusters?
A. Yes, in Windows Server 2003, you can select client-side caching (also know as offline folders) for clustered file shares.
Q. Is the Encrypting File System (EFS) supported on cluster disks?
A. With Windows Server 2003, the encrypting file system (EFS) is supported on clustered file shares. To enable EFS on a clustered file share, you must perform a number of tasks to configure the environment correctly:
EFS can only be enabled on file shares when the virtual server has Kerberos enabled. By default, Kerberos is not enabled on a virtual server. To enable Kerberos you must check the Enable Kerberos Authentication check box on the network name resource that will be used to connect to the clustered file share. NOTE: Enabling Kerberos on a network name has a number of implications that you should ensure you fully understand before checking the box.
All cluster node computer accounts, as well as the virtual server computer account, must be trusted for delegation. See online help for how to do this.
To ensure that the users private keys are available to all nodes in the cluster, you must enable roaming profiles for users who want to store data using EFS. See online help for how to enable roaming profiles.
Once the cluster file shares have been created and the configuration steps above carried out, users data can be stored in encrypted files for added security.
Q. How many file shares can be hosted on a cluster?
A. The number of file shares in a cluster depends on the number of nodes in the cluster and the failure scenarios that you are trying to protect against. A single server has a limit for the number of file shares it can support so you need to take that into account when planning your cluster.
In a 2-node cluster, if one node fails, the remaining node must pick up all of the file shares. Therefore, to ensure the highest availability, the cluster should host the maximum number of shares that can be hosted by a single node.
Note
2-node Server clusters are focused on high availability, not scale-out, therefore you should not expect to hold more shares on a 2-node cluster than a single node.
In a 4-node cluster, you have other options that may be more appropriate, depending on the failure scenarios that you wish to protect against. For example, if you wish to survive one node failing at any point in time, you can configure the shares so that if one node fails, its work is spread across the remaining three nodes. This means that each node could be loaded to 66% of the maximum number of shares and still be within the maximum limit of a single node in the event of a single failure. In this case, the cluster can host three times the number of shares that a single server can host. If you wish to survive two nodes failing, then a 4-node cluster can hold twice as many shares (since if two nodes fail, the remaining two nodes need to pick up the load from the two failed servers) and so on.
In general, as the number of nodes in a cluster increases, the more options you have and the more you can use server clusters to scale-out a highly available infrastructure.
Q. What is the maximum capacity of a cluster disk?
A. Server cluster does not impose any restrictions on the size of a volume supported.
Q. How many disks can Server cluster support?
A. In Windows 2000, each clustered disk had to have a drive letter assigned to it, therefore the maximum number of clustered disks in a single cluster was limited to 23 volumes (26 letters of the alphabet minus A and B [Floppy drives] and C [system/boot drive]).
In Windows Server 2003, there is no longer a requirement for a clustered disk to have a driver letter assigned, therefore the number of disks is limited by the number that can be physically attached and the number supported by the underlying operating system.
Note
Applications can access disks with no drive letters in one of two ways a) directly using the object name associated with the disk or more likely b) by using mount points to link multiple disks together that can be accessed using a single drive letter.
Q. How can a cluster support more disks than there are drive letters?
A. Using file system mount points. For more information about using mount points with clustered disks see the online help for Windows Server 2003.
Q. Why can I browse shares owned by different virtual servers?
A. File shares are not scoped by the virtual server name that is hosting them. If you use a browsing tool (e.g. the NET VIEW command) you will see all the shares that are currently hosted on the physical node.