23.1 NAS and ClearCase

Putting view and (especially) VOB storage on a certified NAS device can provide several advantages:

• Enhanced scalability. VOB or view storage can grow well beyond the physical limits typically imposed when the VOB or view is stored on a ClearCase server host.

• Enhanced flexibility. By separating the VOB server or view server process from the VOB storage, server hosts can be upgraded more easily

• Simplified administration. NAS devices often have enhanced backup and restore features that can simplify this process for ClearCase administrators. When you use the mkstgloc command to create ClearCase server storage location on NAS devices, VOB and view creation and administration can be further simplified.

CAUTION: Every certified NAS device must be specially configured to support remote VOB or view databases. Configuration requirements for each certified device are described in the Release Notes for Rational ClearCase and ClearCase MultiSite. If you do not configure a certified NAS device as described in that document, any VOB or view data stored on that device is at risk. If you put a VOB or view database on a NAS device that has not been certified for this purpose, the data is at risk.

Configuring Network Access to the NAS Device

A NAS device used for VOB or view storage should be on a robust network, preferably on the same subnet as the ClearCase VOB or view server hosts that use it, but at most no more than one hop away. Network access to the NAS device can be configured as follows:

• UNIX VOB or view server hosts must mount the NAS device using an NFS hard mount (the default for most systems). If a soft mount is used, the VOB or view server will fail at startup and write an error message in its log file.

• Windows hosts must establish access to the NAS device with the net use command (or Map Network Drive in the Windows Explorer).

The examples in this chapter assume that you have configured a NAS device on your local area network, and that it can be accessed by UNIX hosts at /net/nasdevice and by Windows hosts at \\nasdevice.

NOTE: Rational only supports use of the NFS protocol to connect a UNIX VOB server host with a VOB database on a NAS device. You must use the CIFS protocol to connect with NAS devices from Windows hosts. Use of NFS software to connect Windows hosts to NAS devices is not supported by Rational.

Changes Are Required in Some Procedures

When a UNIX VOB or view has its database on a NAS device, the ClearCase server process that manages access to the VOB or view runs on a ClearCase host and accesses its storage over the network. This configuration requires several few changes to the standard procedures that we recommend for creating and managing VOBs and views.

Most of the procedural changes described in this chapter are necessary because cleartool commands that deal with creating, registering, or tagging VOB or view storage-including mkvob, mkview, register, mktag, and mkstgloc-need to be invoked with the -host, -hpath, and -gpath options when the VOB or view has its storage on a NAS device.

When run on a UNIX computer, some of these commands generate an informational message indicating that the storage pathname may not reside on the local host.