Describe how Xsan metadata controllers communicate to implement failover

If the metadata controller on your SAN fails for any reason, another computer running Xsan can take over. Metadata controller failover is built into Xsan, unlike many SAN solutions that require you to pay extra for this high-availability feature.

Xsan software includes both the metadata controller and file system client components. Using Xsan administration tools, you can specify the laws of succession, or the order in which Xsan metadata controllers take over for a failed controller. Sophisticated algorithms ensure that succession occurs properly, avoiding split brain, or multiple conflicting metadata controllers. Once the file system clients elect a new metadata controller, the failed system can be deactivated until the problem is resolved.

For high-volume, mission-critical production environments, you may want to dedicate a computer as a standby controller. A standby controller also enables you to update Xsan software without interrupting service to your users.

Describe how to use Xsan Admin to configure an Xsan metadata controller

All computers on the local network that have Xsan installed are listed in the Computers pane. In this step you choose at least one computer to act as metadata controller and set up the others as clients.All computers on the local network that have Xsan installed are listed in the Computers pane. In this step you choose at least one computer to act as metadata controller and
set up the others as clients.

In the Computers pane, select a computer in the list.
If the computer youre looking for is not listed, make sure the Xsan software is installed on it, that it is connected to the SANs Ethernet subnet, and that it is turned on and not
set to sleep.

If the Authenticate button appears, click it and type an administrator user name and password for the computer you are adding to the SAN.

Click Edit.

Choose whether the computer will function as a controller or a client.

You must choose at least one computer to act as controller for the SAN. Choose from the Role pop-up menu:

Client: The computer functions as a client only.
Controller: The computer acts as a controller and is also available for use as a client.

There is no controller-only choice. All controllers are also ready to function as clients.
To prevent a controller from being used as a client, restrict user logins on or physical access to the computer.

If the computer is a controller, choose its failover priority.
Choose High for the primary controller or the only controller in the SAN. Choose Medium or Low for standby controllers.

If this computer is a controller, choose the network interface it will use for metadata communications with other clients and controllers from the Access the SAN via pop- up menu.

Type an Xsan software serial number.

You can find the serial number for a single copy of Xsan on the Xsan installation disc sleeve. If youre using individual licenses for each copy of Xsan, make sure each serial number in the SAN is unique, and leave the Registered to and Organization fields blank.

If you purchased a site-licensed serial number, you can find it on the documentation you received when you purchased the license.

If youre using a site-licensed serial number, type the registered license holder and organization in the Registered to and Organization fields. Be sure to type these exactly as they were provided when you purchased the license.

Click OK, and then repeat these steps for other computers in the list.

When youre through, click Save.

Define an Xsan storage pool

A storage pool is a combination of LUNs. In a small volume it might consist of a single RAID array, but storage pools in many volumes consist of multiple arrays.

Xsan distributes file data in parallel across the LUNs in a storage pool using a RAID 0 (striping) scheme. So, you can improve a clients access speed by distributing available storage over several LUNs in a storage pool.

Within each storage pool in a volume, Xsan stripes file
data across the individual LUNs that make up the storage pool. Once again, performance is improved because data is written in parallel. You can tune SAN performance by adjusting the amount of data written to each LUN in a storage pool (the stripe breadth) to suit a critical application.

Describe how to set up a simple Xsan volume

1 Set up the Fibre Channel network (page 54)
2 Set up the Ethernet network (page 54)
3 Set up SAN users and groups (page 54)
4 Set up LUNs (page 55)
5 Install Xsan software on SAN computers (page 55)
6 Log in to the SAN (page 57)
7 Choose a controller and add clients (page 58)
8 Label and initialize available LUNs (page 61)
9 Create volumes (page 63)
10 Add storage pools to volumes (page 65)
11 Add LUNs to storage pools (page 67)
12 (Optional) Set up status notifications (page 68)
13 (Optional) Assign folders to storage pools (page 69)
14 (Optional) Set user and group quotas (page 71)
15 Start the volumes and mount them on clients (page 73)

List features of Fibre Channel

– eliminates the bottlenecks of traditional network file servers
that use Gigabit Ethernet and that are not fast enough to transfer dense formats such as HD video.

– 2Gb-per-port connection for increased data transfer

– multipathing: Apples Fibre Channel host bus adapters (HBAs) are dual-port cards, providing two connections to the SAN. Fibre Channel multipathing takes advantage of this dual connection: If one Fibre Channel path fails, Xsan continues to use the other for storage accesseliminating a potential single point of failure at the cabling layer. All data paths from the client to the various storage volumes are discovered automatically based on load and availability. This provides two major benefits: Any failure is
handled without affecting the users work, and all paths are load-balanced to ensure maximum performance and reliability.

Describe how a cluster file system takes advantage of a SAN storage architecture

Cluster filesystem – a distributed filesystem that is not a single server with a set of clients, but instead a cluster of servers that all work together to provide high performance service to their clients. To the clients the cluster is transparent – it is just “the filesystem”, but the filesystem software deals with distributing requests to elements of the storage cluster.

Xsan is a 64-bit cluster file system that provides concurrent data access over high- speed Fibre Channel to multiple systems on the network. For better performance and higher availability, you can pool storage across multiple RAID devices, and each
Xsan client can use this centralized data as if it were directly connected. Cluster file systems of this class include SGI Infinite Storage Filesystem CXFS and VERITAS Storage Foundation Cluster File System.

Differentiate between different storage architectures (3). What are some limitations of the first two?

directed-attached storage (DAS)
In a DAS confi guration, disk drives or storage systems are connected directly to a server over SCSI or Fibre Channel. The host server formats the DAS using a compatible disk file system, such as UFS or HFS+, and shares the storage with clients over Ethernet using a network file system, such as AFP, SMB/CIFS, or NFS.

network-attached storage (NAS)
A NAS is a storage device with a built-in computer. This NAS appliance connects to a local area network and, like a DAS, shares storage with clients over Ethernet using a network file system. A NAS appliance typically features a specialized server operating system designed to make file-sharing setup and maintenance easier than with most general-purpose servers.

storage area network (SAN)
A storage area network, or SAN, is a method of aggregating storage devices and allowing servers and client computers to access them as a single virtual storage entity. The volume looks just like a DASlike a big hard driveto the servers. The difference is
that, with a SAN file system such as Xsan, all the servers can access the storage volume at the same time. These host servers can then share the data with additional clients on the local Ethernet network using a network fi le system, such as AFP, SMB/CIFS, or NFS.

Limitations of DAS and NAS systems: (1) Single point of failure; (2) Performance bottlenecks (all file systems must go through a single workstation or server); (3) Difficult scalability (limited by # of devices that can be attached to the server)

Explain the benefits of storage networking

XSan provides fast, concurrent access to terabytes of
centralized data. Combining it with Xserve RAID arrays and slices you can deploy large, easy-to-expand volumes of storage that clients use like local disks but are actually shared over a high-speed Fibre Channel fabric.

OS X Server – Editing the default set of folders created within a user’s home directory when a new user is created

/System/Library/User Template/English.lproj/