Storage device support for ClearCase

Content

The three generic types of storage available today are as follows:

• Direct Attached Storage (DAS)

Storage (usually disk or tape) is directly attached by cable to the computer processor. The hard disk drive inside a PC or as tape drive attached to a single server are simple types of DAS. Input/Output (I/O) requests access the device directly.




• Storage Area Network (SAN)

SAN is a high-speed sub-network of shared storage devices. A storage device is a host that contains nothing but a disk or array of disks for storing data.

A SAN's architecture works in a way that makes all storage devices available to all servers on a local area network (LAN) or wide area network (WAN). As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. In this environment, the server merely acts as a pathway between the end user and the SAN.

Because stored data does not reside directly on a server other than the SAN, the server's power is utilized for business applications, and network capacity is released to the end user.



• Network Attached Storage (NAS)

A NAS device (also known as appliance or filer), which is usually an integrated processor plus disk storage, is attached to a TCP/IP based local area network (LAN) or wide area network (WAN) and accessed using specialized file access and file sharing protocols. File requests received by a NAS are translated by the internal processor to device requests.

What is supported by ClearCase?

• ClearCase supports DAS as long as the host operating system is supported. Review the Related Information section below for more details.
  
  
• ClearCase supports SANs as long as the host operating system is supported. Review the Related Information section below for more details. Most SAN solutions rely on switching technology for protocol implementation, in conjunction with fiber channel. This is similar to a DAS configuration. Oplocks need to be disabled for Unix file systems that contain ClearCase storage. Oplocks are supported in a Windows only environment for ClearCase storage.
  
  
• For a description of the ClearCase NAS support policy, refer to technote http://www-01.ibm.com/support/docview.wss?uid=swg21971394.