Tb Limitation; Cache Policy - Promise Technology VessRAID 1740s Product Manual

VessRAID 1740s, 1840s 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

As it is used with VessRAID, the term cache refers to any of several kinds of high-
speed, 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, user-
adjustable 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 105
(WebPAM PROe) or page 149 (CLU)
• On an existing logical drive. See "Making Logical Drive Settings" on
page 113 (WebPAM PROe) or "Setting Write Cache Policy" on page 154
(CLU)
Logical Drive Size
8 to 16 TB
4 to 8 TB
2 to 4 TB
0 to 2 TB
Sector Size
4096 bytes (4 KB)
2048 bytes (2 KB)
1024 bytes (1 KB)
512 bytes (512 B)
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