Kofax Communication Server 9.1.1 - Manual (Page 77)

Environment Guide Version 3.00.04
© Copyright Kofax, Inc. All information is subject to change without notice. 77
The average 2009 desktop hard disk has seek times of 9 or 10 milliseconds, while a fast server-grade hard
disk may show seek times of 2 to 4 milliseconds. The average latency (half a revolution) can be calculated
from the rotational speed of the disk:
RPM 5400 7200 10000 15000
Average latency 5.6 ms 4.2 ms 3 ms 2 ms
Here are some hard disk performance examples:
Hard disk RPM Latency Avg seek time Writes / sec
WD Caviar Blue 250 GB 7200 4.2 ms 8.9 ms 76
HP SAS enterprise 10000 rpm 10000 3 ms 4 ms 143
HP SAS enterprise 15000 rpm 15000 2 ms 3 ms 200
Hard Disk Write Cache
The hard disk write cache setting can be looked up under Drive – Properties – Hardware – Properties –
Policies:
Enable write caching on the disk only if the KCS is connected to an uninterruptible power supply (UPS).
Otherwise power failures may leave the TCOSS file system in an inconsistent state.
Write caching on the disk improves the speed of random writes considerably, for a rough estimate take a
factor of 2.
HW RAID Configurations
For increased disk throughput use a HW RAID configuration in combination with battery-backed write cache
on the disk controller.