VOB host configuration guidelines

Properly configured VOB hosts are essential to obtaining satisfactory DevOps Code ClearCase® performance.

Any host on which a vob_server process runs is a VOB host and a DevOps Code ClearCase community might have many VOB hosts.

As described in DevOps Code ClearCase server processes, a VOB host runs a number of server processes for each VOB it supports. Because an active VOB host might have to support dozens, or even hundreds, of such processes, and support network access from many clients, follow the guidelines in this section when specifying the hosts's physical memory, storage, processor, and network interface hardware. In addition, you might want to use the performance tuning procedures described in Improving VOB host performance.

Note: For Windows®, the VOB host must run the server, rather than the workstation, variant of the operating system (Windows 2000 Server, for example). The workstation variants of these operating systems limit the number of concurrent client connections and are not appropriate for most VOB host applications.

Physical memory

The memory requirements for a VOB server need to be sufficient for these purposes:

The data and instruction space needs of DevOps Code ClearCase processes (1 albd_server, v vob_servers and 5v vobrpc_servers, where v is the number of VOBs, and d db_servers, where d is the maximum number of simultaneous users).
Sufficient file-system cache to accommodate the working set of VOB database pages accessed during normal daily activity.

Adequate physical memory is the most important factor in VOB performance; increasing the size of a VOB host's main memory is the easiest (and most cost-effective) way to make VOB access faster and to increase the number of concurrent users without degrading performance.

Note: Do not run view_server processes on a VOB host (see Minimize process overhead).

Swap space

On a VOB server host, the recommended amount of swap space is equal to handle these processes:

The maximum number of db_servers multiplied by the size of each db_server process (approximately 5 MB)
The maximum number of vobrpc_servers multiplied by the size of each vobrpc_server process (approximately 10 MB)

The maximum number of db_servers must be equal to the maximum number of simultaneous users of all VOBs on the VOB server, and the maximum number of vobrpc_servers is equal to the number of VOBs hosted on the VOB server multiplied by 5. For example, a Solaris VOB host must accommodate 200 VOBs and 300 simultaneous users. The recommended amount of swap space is 200*10MB = 2 GB, plus 300*5 MB = 1.5 GB, or 3.5 GB.

Disk capacity

A VOB database (and, on Windows, the entire VOB storage directory) must fit in a single disk partition. VOB databases tend to grow significantly as development proceeds and projects mature. Although there is no general guidance for estimating how large a VOB will be, Estimating VOB size provides some guidelines that might be useful is establishing VOB server disk capacity requirements.

Use a high-performance disk subsystem with high rotational speed, low seek times, and a high mean time between failures. If possible, use a RAID or similar system that takes advantage of disk striping and mirroring. Mirrors are useful for backups, although there is a slight performance degradation associated with their use. However, striping helps overall performance and more than makes up for any degradation caused by mirroring. For more information, see Maximize disk performance.

Processor capacity

A VOB host must have adequate CPU capacity. The definition of adequate in this context varies from one hardware architecture to another. With DevOps Code ClearCase and similar enterprise applications, server CPU capacity is a critical factor governing performance of client operations. Make the most of the available server CPU cycles by keeping nonessential processes, including DevOps Code ClearCase client tools and views, off the VOB host.

Network connectivity

Nearly every access to a VOB places a load on the VOB host's network interface; a high-bandwidth (100 MB/sec. or greater) network connection to the VOB host is important. Multiple network interfaces to a VOB host can further improve its network accessibility, but some operating systems require each such connection to have a separate host name, which in turn requires the use of multiple regions in the DevOps Code ClearCase registry (see Administering the DevOps Code ClearCase registry).