Product manual

Chapter 7: Technology Background
281
Stripe Size
Stripe Size, also called “Stripe Block Size,” refers to the size of the data blocks
written to, and read from, the physical drives. Stripe Size is specified when you
create a logical drive. You can choose Stripe Size directly when you use the
Wizard Advanced Configuration function to create a logical drive.
You cannot change the Stripe Size of an existing logical drive. You must delete
the logical drive and create a new one.
The available Stripe Sizes are 64 KB, 128 KB, 256 KB, 512 KB, and 1 MB. 64 KB
is the default. There are two issues to consider when choosing the Stripe Size:
• You should choose a Stripe Size equal to, or smaller than, the smallest
cache buffer found on any physical drive in the disk array. Selecting a larger
value slows read/write performance because physical drives with smaller
cache buffers need more time for multiple accesses to fill their buffers.
• 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 Size.
If you do not know the cache buffer or fixed data block sizes, choose 64 KB as
your Stripe Size. Generally speaking,
• Email, POS, and web servers prefer smaller stripe sizes.
• Video and database applications prefer larger stripe sizes.
Sector Size
A sector is the smallest addressable area on a physical drive. Sector size refers
to the number of data bytes a sector can hold. A smaller sector size is a more
efficient use of a physical drive’s capacity. 512 bytes (512 B) is the most common
sector size, and the default in WebPAM PROe.
Preferred Controller ID
When you create a logical drive using the Advanced method of disk array
creation, you can specify the Preferred Controller ID:
• Controller 1 – Assign all logical drives to Controller 1
• Controller 2 – Assign all logical drives to Controller 2.
• Automatic – Alternate logical drive assignments between Controllers 1
and 2.
Automatic is the default and preferred setting because it balances the logical
drive assignments for you.
See “Creating a Disk Array Manually” on page 122, “Creating a Disk Array with
the Wizard” on page 123, and “Creating a Disk Array – Advanced” on page 183.