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DCSE: PowerEdge 1550 Self-Study Version 0.3, 4 December, 2000
Page 78 Dell
The fourth page is the Logical Drive Definition page. It provides the
facility for setting:
• Raid Level: options are 0, 1, or 5.
• Stripe Size: this defines the size of the data block written to each disk in a
logical drive. Larger stripe sizes provide better performance during
sequential read transactions. For random reads select a smaller stripe size.
The default is 64 KB.
• Read Policy: options are normal, read-ahead, or adaptive. Normal
specifies that the controller does not use read-ahead for the current logical
drive. Read-ahead specifies that the controller uses read-ahead for the
current logical drive. Adaptive specifies that the controller begins using
read-ahead if the two most recent disk access occurred un sequential
sectors. If all requests are random the algorithm reverts to normal,
however, all requests are still evaluated for possible sequential operation.
This is the default setting.
• Write Policy: sets the write policy to write-back or write-through. When
set to write-back the controller sends a transfer completion signal after the
controller cache has received all of the data in a transaction. When set to
write-through the controller sends the transfer completion signal after all
of the data in a transaction has been written to the logical drive.
• Cache Policy: specify if reads are to be buffered in cache memory
(Cached I/O) or not (Direct I/O). Cached I/O is the default setting.
• Span: options depend on if the configuration will support spanning.
Spanning is the ability for an array to cross channels. If there are drives
on more than one channel then the options are Enable or Disable.
Otherwise, the only option is Disable.
• Select Size: This is where the size of the array is specified. There are
options to the right of this item advising what the size should be based on
different sections made such as Raid Level. Click in the text box supplied
and type the appropriate size, the size entered must agree with the Raid
Level selected otherwise when the size is entered and Next is clicked the
page will redisplay with the Select Size textbox cleared.
Make the selection required for the array being defined then click Accept
to accept the changes. Clicking Reset will undo the settings selected.
Click Next to continue onto the next and final page to the wizard.