Service manual

Sizing Disk Subsystems
90 Sun ONE Directory Server Installation and Tuning Guide • June 2003
Cache Files on Memory Based File Systems
In a tmpfs file system, for example, files are swapped to disk only when physical
memory is exhausted. Given sufficient memory to hold all cache files in physical
memory,you may derive improved performance by allocating equivalent disk
space for a
tmpfs file system on Solaris platforms or other memory based file
systems such as RAM disks for other platforms, and setting the value of
nsslapd-db-home-directory to have the Directory Server store cache files on that
filesystem.Thisprevents thesystem from unnecessarily flushingmemory mapped
cachefilestodisk.
Disk Subsystem Alternatives
“Fast, cheap, safe: pick any two.”—Sun Performance and Tuning, Cockroft and Pettit.
Fast and Safe
When implementing a deployment in which both performance and uptime are
critical, consider hardware-based RAID controllers having non-volatile memory
caches to provide high speed buffered I/O distributed across large arrays of disks.
By spreading load across many spindles and buffering access over very fast
connections, I/O can be optimized, and excellent stability provided through high
performance RAID striping or parity blocks.
Large non-volatile I/O buffers and high performance disk subsystems such as
those offered in Sun StorEdge™ products can greatly enhance Directory Server
performance and uptime.
Fast write cache cards provide potential write performance improvements,
especially when dedicated for transaction log use. Fast write cache cards provide
non-volatile memory cache that is independent from the disk controller.
Fast and Cheap
For fast, low-cost performance, ensure you have adequate capacity distributed
across a number of disks. Consider disks having high rotation speed and low seek
times. For best results, dedicate one disk to each distributed component. Consider
using multi-master replication to avoid single points of failure.
Cheap and Safe
For cheap, safe configurations, considerlow-cost, software-based RAID controllers
such as Solaris Volume Manager.