Promise Technology EX8650, EX8658, EX8654, EX4650 Choosing Stripe Block Size, Choosing Sector Size

SuperTrak EX Series User Manual

Choosing Stripe Block Size

You set the stripe block size, also called block size, when you create a logical drive. With SuperTrak, the choices are 64 KB, 128 KB, 256 KB, 512 KB, and 1024 KB. 64 KB is the default.

Your choice will directly affect performance. There are two issues to consider when choosing the stripe block size.

•Choose a stripe block size equal to or smaller than the smallest cache buffer found on any physical drive in your logical drive.

A larger value slows the logical drive down because physical drives with smaller cache buffers need more time for multiple accesses to fill their buffers.

•If your data retrieval consists of fixed-size data blocks, such as some database and video applications, choose that data block size as your stripe block size.

Generally speaking, email, POS, and webservers prefer smaller stripe block sizes. Video and database applications prefer larger stripe block sizes.

See “Creating a Logical Drive” on page 93 and “Creating a Logical Drive” on page 159, and “Creating a Disk Array – Advanced Configuration” on page 155.

Choosing Sector Size

You set the sector size when you create a logical drive. With SuperTrak, the choices are 512 B, 1 KB, 2 KB, and 4 KB. 512 B is the default.

A sector is the smallest addressable area on a physical drive. Sector Size refers to the size of sector measured by the number of bytes of data it can hold. The most common sector size is 512 bytes (512 B). A smaller sector size results in a more efficient use of a physical drive’s capacity. 512 B is the default sector size for logical drives on SuperTrak.

The number of usable sectors is limited by the addressing method of the computer's operating system:

•Windows XP (32-bit) support 10-bit logical bit addressing (LBA), so with 512 B sectors, they can only support up to 2 terabytes (TB) of data storage capacity. To increase the capacity, you must use larger sectors. See “2 TB Limitation” on page 237.

•Windows XP (64-bit), Windows Server 2003 and 2008, and Windows Vista support 64-bit LBA, so they are not affected by this limitation. For these OSes, always choose the default 512 B sector size.

•Linux operating systems with the 2.4 kernel do not support variable sector sizes. For these OSes, always choose the default 512 B sector size.

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