Promise Technology TX4 User Manual

UltraTrak100 TX4 and UltraTrak100 TX8  User Manual 

For the Gigabyte Boundary feature to work, the Gigabyte Boundary feature must 
be set to ON when the original array is created. When enabled, the Gigabyte 
Boundary feature rounds the drive capacity of all drives to the common whole GB 
drive size. For example, with the Gigabyte Boundary feature enabled, the 
remaining working drives can be 20.5 GB and the replacement drive can be 20.3, 
since all are rounded down to 20GB. This permits the smaller drive to be used. 
Please note that users will lose a small amount of available storage capacity from 
each drives in order to arrive at a common drive size. 

There are two issues to consider when selecting the Stripe Block Size. 

First, you should choose a Stripe Block Size equal-to or smaller than the smallest 
cache buffer found on any array disk drive. Selecting a larger value slows the 
array down because disk drives with smaller cache buffers need more time for 
multiple accesses to fill their buffers.  

Secondly, if your data retrieval consists of fixed data blocks, such as with some 
database or video applications – then you should choose that size as your Stripe 
Block Size. 

There are several issues to consider when choosing the RAID Level for your 
UltraTrak100 array.  Appendix A - Technology Background on page 41 gives 
some technical insight regarding each RAID choice and the following discussion 
summarizes some advantages, disadvantages and applications for each choice. 

Implements a striped disk array, the data is 
broken down into blocks and each block is 
written to a separate disk drive 

I/O performance is greatly improved by 
spreading the I/O load across many 
channels and drives 

No parity calculation overhead is involved 

Not a "True" RAID because it is not fault-
tolerant 

The failure of just one drive will result in all 
data in an array being lost 

Should not be used in mission critical 
environments 

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Image Editing 

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Pre-Press Applications 

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Any application requiring high bandwidth 

Simplest RAID storage subsystem design 

Can increase read performance by 
processing data requests in parallel since 
the same data resides on two different 
drives  

High disk overhead  - uses only 50% of 
total capacity