ATI Xpert 98 User Manual - Page 109

JBOD, Choosing Stripe Block Size, Gigabyte Boundary

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Chapter 6: Technology Background JBOD Advantages Disadvantages Enables you to manage multiple physical drives from a single controller The failure of just one drive will result in all data in all drives being lost Not suitable for mission critical environments Recommended Applications for JBOD: • Any application requiring large data capacity but where read/write speed or fault-tolerance are not important • Applications were low-cost operation critical Choosing Stripe Block Size For RAID 0, 5, and 10 logical drives, the stripe block size value can be set to 64 KB or 128 KB. 64 KB is the default. Your choice will directly affect performance. There are two issues to consider when selecting 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. Gigabyte Boundary The Gigabyte Boundary feature is designed for logical drives in which a drive has failed and the user cannot replace the drive with the same capacity or larger. Instead, the Gigabyte Boundary feature permits the installation of a replacement drive that is slightly smaller (within 1 gigabyte) than the remaining working drive (for example, an 80.5-GB drive would be rounded down to 80 GB). This can be helpful in the event that a drive fails and an exact replacement model is no longer available. Gigabyte Boundary is available for all RAID levels. If you split the capacity of your physical drives between two logical drives, you can choose Gigabyte Boundary for the second logical drive. See "Creating a Logical Drive" on page 62. 103

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Chapter 6: Technology Background
103
JBOD
Recommended Applications for JBOD:
•
Any application requiring large data capacity but where read/write speed or
fault-tolerance are not important
•
Applications were low-cost operation critical
Choosing Stripe Block Size
For RAID 0, 5, and 10 logical drives, the stripe block size value can be set to
64 KB or 128 KB. 64 KB is the default. Your choice will directly affect
performance. There are two issues to consider when selecting 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.
Gigabyte Boundary
The Gigabyte Boundary feature is designed for logical drives in which a drive has
failed and the user cannot replace the drive with the same capacity or larger.
Instead, the Gigabyte Boundary feature permits the installation of a replacement
drive that is slightly smaller (within 1 gigabyte) than the remaining working drive
(for example, an 80.5-GB drive would be rounded down to 80 GB). This can be
helpful in the event that a drive fails and an exact replacement model is no longer
available.
Gigabyte Boundary is available for all RAID levels. If you split the capacity of your
physical drives between two logical drives, you can choose Gigabyte Boundary
for the second logical drive. See “Creating a Logical Drive” on page 62.
Advantages
Disadvantages
Enables you to manage multiple
physical drives from a single controller
The failure of just one drive will result in
all data in all drives being lost
Not suitable for mission critical
environments