VTrak E-Class Product Manual - Promise Technology, Inc.

VTrak E-Class Product Manual
• Linux operating systems with the 2.6 kernel support 64-bit LBA. For these
OSes, always choose the default 512 B sector size.
2 TB Limitation
If your Host PC runs Windows 2000 or Windows XP (32-bit), and you want to
create logical drives larger than 2TB, you must choose a sector size larger than
512 B when you create the logical drive. The table below correlates sector size
with logical drive capacity.
Because logical drives can be expanded, you may encounter a situation where
the usable capacity of your expanded logical drive is reduced by the addressing
issue described above. There are two alternatives:
• Limit your logical drive expansion to within the limits described in the chart.
• Back up your data, then delete your existing logical drive and create a new
one with a larger sector size.
Cache Policy
Logical Drive Size Sector Size
8 to 16 TB 4096 bytes (4 KB)
4 to 8 TB 2048 bytes (2 KB)
2 to 4 TB 1024 bytes (1 KB)
0 to 2 TB 512 bytes (512 B)
As it is used with VTrak, the term cache refers to any of several kinds of highspeed,
volatile memory that hold data moving from your computer to the physical
drives or vice-versa. Cache is important because it can read and write data much
faster than a physical drive. There are read caches, which hold data as it is read
from a physical drive; and write caches, which hold data as it is written to a
physical drive.
In order to tune the cache for best performance in different applications, useradjustable
settings are provided. Cache settings are made in conjunction with
logical drives:
• When you create a logical drive. See “Creating a Logical Drive” on page 127
or page 174
• On an existing logical drive. See “Making Logical Drive Settings” on
page 136 or “Setting Write Cache Policy” on page 176
246