Optimum Controller Settings For Cachecade; Optimum Controller Settings For Fast Path; Creating A Virtual Drive Using Simple Configuration - Lenovo ThinkServer RD650 User Manual

12Gb/s MegaRAID SAS Software User Guide
March 2014
No read ahead: (the default) Disables the read ahead capability.
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Write policy: Specify the write policy for this virtual drive:

Write Through: In this mode, the controller sends a data transfer completion signal to the host when the
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drive subsystem has received all of the data in a transaction. This option eliminates the risk of losing cached
data in case of a power failure.
Always Write Back: In this mode, the controller sends a data transfer completion signal to the host when the
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controller cache has received all of the data in a transaction.
Write Back with BBU: (the default) In this mode, the controller enables write back caching when the battery
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backup unit (BBU) is installed and charged. This option provides a good balance between data protection
and performance.
I/O policy: The I/O policy applies to reads on a specific virtual drive. It does not affect the read ahead cache.

Cached IO: In this mode, all reads are buffered in cache memory.
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Direct IO: (the default) In this mode, reads are not buffered in cache memory. Data is transferred to the cache
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and the host concurrently. If the same data block is read again, it comes from cache memory.
Cached IO provides faster processing, and Direct IO ensures that the cache and the host contain the same data.
Access policy: Select the type of data access that is allowed for this virtual drive.

Read/Write: (the default) Allow read/write access. This setting is the default value.
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Read Only: Allow read-only access.
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Blocked: Do not allow access.
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Disk cache policy: Select a cache setting for this drive:

Enabled: Enable the disk cache.
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Disabled: (the default) Disable the disk cache.
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Unchanged: Leave the current disk cache policy unchanged.
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9.1.2

Optimum Controller Settings for CacheCade

Write Policy: Write Back/Write Through/Always Write Back
9.1.3

Optimum Controller Settings for Fast Path

Write Policy: Write Through
IO Policy: Direct IO
Read Policy: No Read Ahead
Stripe Size: 64 KB
9.1.4

Creating a Virtual Drive Using Simple Configuration

Simple configuration is the quickest and easiest way to create a new storage configuration. When you select the
simple configuration mode, the system creates the best configuration possible using the available drives.
NOTE The write policy depends on the status of the BBU. If the BBU is not
present, is low, is failed, or is being charged, the current write policy
switches to write through, which provides better data protection.
NOTE You cannot create spanned drives using the simple configuration
procedure. To create spanned drives, use the advanced configuration
LSI Corporation
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Chapter 9: Configuration
Creating a New Configuration