Promise Technology 66 Pro - Manual (Page 114)

SuperTrak66™ User's Manual Chapter 6
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6.1 Application Scenarios
This section describes typical application scenarios for a RAID system. You may
use this information as a guideline to tailor your RAID system configuration to meet
your specific needs.
Keep in mind that when dealing with striped arrays, a larger stripe block size
typically benefits arrays that tend to receive more random/smaller I/O requests.
This is because such a setting tends to minimize seeks for a small request down
to a single I/O operation. In contrast, a small stripe block size setting typically
benefits arrays which tend to receive more sequential/larger I/O requests. This is
because such a setting maximizes throughput by employing the data transfers of
all drives simultaneously.
NOTE: Though the following configurations recommend different RAID levels,
RAID 3 is recommended in most single-threaded (non-server) desktop PC
operations.
High Performance Desktop PCs Working With Large Files
For video editing or desktop publishing PC stations where large files are stored on
the hard drive, the need for performance outweighs that of data security. Accessing
such large files requires sequential data transfers where performance can be
improved by using striping (RAID Level 0). An ideal setup would have the large data
files stored on the striped array, and the operating system boot drive using a
separate disk controller (i.e. onboard motherboard controller).
When defining such an array, remember that a small stripe block size (such as
64KB) typically benefits arrays which tend to receive more sequential/large I/O
requests (such as those used in video editing) since it maximizes throughput by
employing the transfer of all drives simultaneously. The more drives assigned to
this array, the better the throughput potential will be. Bear in mind, there are no
fault tolerant data protection features provided in a RAID 0 array. It is exclusively
geared towards gaining data transfer performance.
Corporate Desktop PC Requiring Data Protection
Under Windows NT, users have the option of enabling fault tolerance through
software. SuperTrak66 permits a bootable, hardware-based fault tolerant solution to
secure data from drive failure. RAID Level 3 offers the largest data capacity while
maintaining fault tolerance using parity information. RAID 0+1 is also
recommended since it offers higher data throughput and dual fault tolerance though
it is more expensive in terms of drives.
Windows NT File Server
Windows NT tends to work heavily with large swap files for virtual memory. Under
such a heavy load, the swap file I/Os undergo intensive activity. If the user's data
files and the system files are located on the same drive, then the system
performance is typically degraded because of the swap files.