User Guide

Optimizing Server Memory 21
Server Memory Administration Guide
103-000147-001
August 30, 2001
Novell Confidential
Manual 99a38 July 17, 2001
60 percent. If you are using mostly NSS volumes, you can run at a much
higher percentage, such as 85 to 90 percent.
 Closefilecachesize dictates how many closed files are kept in cache. The
recommended minimum is 50,000.
 Fileflushtimer and Bufferflushtimer Increasing these parameters from
their defaults helps the caching up to a certain point, but too much
increase causes a throttling problem with writing out the metadata. This
is somewhat dependent on processor speed and disk speed, so you could
try adjusting them for your system. If NSS performance is very poor, 75
might be too high and you could try 50. If performance is just below
normal, you could try increasing the values a little.
To activate these parameters, you can issue the following command at the
startup of NSS, or place it in the AUTOEXEC.NCF file:
nss /cachebalance=80 /fileflushtimer=75 /bufferflushtimer=75
/closedfilecachesize=50000
For more information on setting Cache Buffers for NSS, see Setting the Cache
Buffers in the Novell Storage Services Administration Guide.
Traditional File System
Because it is much faster to get data from memory than to get it from disk,
caching frequently requested data increases server performance. The more
RAM installed in the server, the more cache memory is available. Cache hits
occur when a client requests data and the server supplies the data from cache
memory instead of from disk. The least recently used algorithm determines
whether data is kept in cache memory or written to disk.
File cache buffers are organized into a linked list. Most recently used (MRU)
buffers are at the head of the list and least recently used (LRU) buffers are at
the tail of the list. The length of time the oldest buffer has been in the list is
shown as the LRU Sitting Time statistic.
In tuning file cache for the traditional file system, the goal is to determine how
much memory the server needs so that recently accessed data can always be
retrieved from cache. Monitoring the LRU Sitting Time statistic is key to
tuning file cache.
Understanding LRU Sitting Time
The LRU Sitting Time status is updated and displayed once per second. The
statistic is calculated by taking the difference between the current time and the