3Ware 9650SE-2LPB-10 User Manual page 108

Chapter 8. Configuring Units
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Note:
Creating a unit erases all data on all drives. Although creating a RAID 1
(mirror) creates a unit that will have a duplicate of data on both drives after it is put
in use, creating a RAID 1 cannot be used to make a backup copy of data that
currently exists on a single drive unless you migrate from a RAID 1 to two individual
single disks.
Name of the unit (optional)
Units can be given names. These names will be visible in 3DM and, 3BM.
Stripe size, if appropriate for the RAID level
In general, smaller stripe sizes are better for sequential I/O, such as video, and
larger stripe sizes are better for random I/O (such as databases).
Striping size is not applicable for RAID 1, because it is a mirrored array
without striping.
Using the default stripe size of 64KB usually gives you the best performance
for mixed I/Os. If your application has some specific I/O pattern (purely
sequential or purely random), you might want to experiment with a smaller or
larger stripe size.
Unit policies
Several unit policies are set when you create a new unit:
• Write Cache (enabled, by default)
• Drive Queuing (disabled, by default)
• Auto Verify (disabled, by default)
• Continue on Source Error During Rebuild (disabled, by default)
• StorSave Profile (Protection, by default)
The particular policies that you can adjust when you create the unit vary,
depending on which program you are using: 3DM, 3BM, or the CLI.
• In 3DM and the CLI, you can enable/disable write cache, enable Auto-
Verify, and specify whether to continue on source error
• In 3BM, you can specify all policies except Auto-Verify
You can change all of these policies after the unit has been created.
For a summary of what these policies do, see the discussion under "Setting
Unit Policies" on page 111. For how to adjust each one, see the procedures
later in this chapter.
3ware Serial ATA RAID Controller User Guide