Asus SCSI 320-0 Global Array Manager Transition Tool - Page 57

Action, Write Policy, Cache Policy, Select the Cache Policy.

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Configuration Wizard, Continued Step 4 Select the Write Policy. Action Write Policy This parameter specifies the cache write policy. You can set the write policy to write-back or write-through. In Write-back caching, the controller sends a data transfer completion signal to the host when the controller cache has received all the data in a transaction. In Write-through caching, the controller sends a data transfer completion signal to the host when the disk subsystem has received all the data in a transaction. This is the default setting. Write-through caching has a data security advantage over write-back caching, whereas write-back caching has a performance advantage over write-through caching. You should not use write-back for any logical drive to be used as a Novell NetWare volume. 5 Select the Cache Policy. Cache Policy This parameter applies to reads on a specific logical drive. It does not affect the Read ahead cache. Cached I/O specifies that all reads are buffered in cache memory. This is the default setting. Direct I/O specifies that reads are not buffered in cache memory. Direct I/O does not override the cache policy settings. Data is transferred to cache and the host concurrently. If the same data block is read again, it comes from cache memory. 6 Enable or disable the spanning mode for the current logical drive. If enabled, the logical drive can occupy space in more than one array. If disabled, the logical drive can occupy space in only one array. For two arrays to be spannable, they must have the same stripe width (they must contain the same number of physical drives) and must be consecutively numbered. For example, assuming Array 2 contains four disk drives, it can be spanned only with Array 1 and/or Array 3, and only if Arrays 1 and 3 also contain four disk drives. If the two criteria for spanning are met, MegaRAID automatically allows spanning. If the criteria are not met, the Span setting makes no difference for the current logical drive. 7 Select the size of the logical drive in MB. 8 Click on the Accept button to accept the changes or click on the Reset button to delete the changes and return to the previous settings. Cont'd Chapter 3 WebBIOS Configuration Utility 49

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Chapter 3 WebBIOS Configuration Utility
49
Configuration Wizard,
Continued
Step
Action
4
Select the Write Policy.
Write Policy
This parameter specifies the cache write policy. You can set the write policy
to write-back or write-through.
In
Write-back
caching, the controller sends a data transfer completion signal to the host
when the controller cache has received all the data in a transaction.
In
Write-through
caching, the controller sends a data transfer completion signal to the host
when the disk subsystem has received all the data in a transaction. This is the default
setting.
Write-through caching has a data security advantage over write-back caching, whereas
write-back caching has a performance advantage over write-through caching.
You should
not use write-back for any logical drive to be used as a Novell NetWare volume.
5
Select the Cache Policy.
Cache Policy
This parameter applies to reads on a specific logical drive. It does not affect
the Read ahead cache.
Cached I/O
specifies that all reads are buffered in cache memory. This is the default
setting.
Direct I/O
specifies that reads are not buffered in cache memory. Direct I/O does not
override the cache policy settings. Data is transferred to cache and the host concurrently.
If the same data block is read again, it comes from cache memory.
6
Enable or disable the spanning mode for the current logical drive. If enabled, the logical
drive can occupy space in more than one array. If disabled, the logical drive can occupy
space in only one array.
For two arrays to be spannable, they must have the same stripe width (they must contain
the same number of physical drives) and must be consecutively numbered. For example,
assuming Array 2 contains four disk drives, it can be spanned only with Array 1 and/or
Array 3, and only if Arrays 1 and 3 also contain four disk drives. If the two criteria for
spanning are met, MegaRAID automatically allows spanning. If the criteria are not met,
the
Span
setting makes no difference for the current logical drive.
7
Select the size of the logical drive in MB.
8
Click on the
Accept
button to accept the changes or click on the
Reset
button to delete the
changes and return to the previous settings.
Cont’d