Creating a New Unitwww.3ware.com 127Stripe size, if appropriate for the RAID levelIn general, smaller stripe sizes are better for sequential I/O, such as video, andlarger stripe sizes are better for random I/O (such as databases).Striping size is not applicable for RAID 1, because it is a mirrored arraywithout striping.Using the default stripe size of 64KB usually gives you the best performancefor mixed I/Os. If your application has some specific I/O pattern (purelysequential or purely random), you might want to experiment with smaller orlarger stripe size.Unit policiesSeveral unit policies are set when you create a new unit: Write Cache (enabled, by default) Drive Queuing (enabled, by default) (9550SX controllers only) Auto-Verify (disabled, by default) Continue on Source Error When Rebuild (disabled, by default)Does not apply to 9550SX controllers, as this feature is integrated into theStorSave Profile. StorSave Profile (Protection, by default) (9550SX controllers only)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 using the CLI, you can enable/disable write cache, enableAuto-Verify, and specify whether to continue on source error In 3BM, you can specify all policies except Auto-VerifyYou can change all of these policies after the unit has been created.For a summary of what these policies do, see the discussion under “UnitPolicies” on page 93 in the section “Controller Settings Page”. For how toadjust each one, see the procedures later in this chapter.Creating a Unit through 3DMIn 3DM, configuration starts from the Maintenance page (Figure 51), whereyou can configure a new unit, designate an available drive as a hot spare,delete a unit, and remove units or drives. You can also have 3DM rescan thecontroller, if you have added drives or units.For information about working in 3DM, see “3ware Disk Manager (3DM 2)”on page 65.
