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the relative amount of time it spends in I/O versus CPU activity. Studies have shown that
doubling the number of CPUs increases servlet performance by 50 to 80 percent.
Memory
See the section Hardware and Software Requirements in the Sun Java System Application Server
Release Notes for specic memory recommendations for each supported operating system.
Disk Space
It is best to have enough disk space for the OS, document tree, and log les. In most cases 2GB
total is sucient.
Put the OS, swap/paging le, Enterprise Server logs, and document tree each on separate hard
drives. This way, if the log les ll up the log drive, the OS does not suer. Also, its easy to tell if
the OS paging le is causing drive activity, for example.
OS vendors generally provide specic recommendations for how much swap or paging space to
allocate. Based on Sun testing, Enterprise Server performs best with swap space equal to RAM,
plus enough to map the document tree.
Networking
To determine the bandwidth the application needs, determine the following values:
■
The number of peak concurrent users (N
peak
) the server needs to handle.
■
The average request size on your site, r. The average request can include multiple
documents. When in doubt, use the home page and all its associated les and graphics.
■
Decide how long, t, the average user will be willing to wait for a document at peak
utilization.
Then, the bandwidth required is:
N
peak
r / t
For example, to support a peak of 50 users with an average document size of 24 Kbytes, and
transferring each document in an average of 5 seconds, requires 240 Kbytes (1920 Kbit/s). So
the site needs two T1 lines (each 1544 Kbit/s). This bandwidth also allows some overhead for
growth.
The server’s network interface card must support more than the WAN to which it is connected.
For example, if you have up to three T1 lines, you can get by with a 10BaseT interface. Up to a
T3 line (45 Mbit/s), you can use 100BaseT. But if you have more than 50 Mbit/s of WAN
bandwidth, consider conguring multiple 100BaseT interfaces, or look at Gigabit Ethernet
technology.
Server Scaling
SunGlassFishEnterpriseServer2.1PerformanceTuningGuide • January200994