Product manual

Chapter 7: Technology Background
291
Preferred Controller ID
See “Preferred Controller ID” on page 281.
Power Saving
Power saving is a method of conserving energy by applying specific actions to
hard disk drives (HDD). After an HDD has been idle for the set period of time, you
can elect to:
• Parking the read/write heads – Referred to as Power Saving Idle Time on
VTrak.
• Reducing disk rotation speed – Referred to as Power Saving Standby Time
on VTrak.
• Spinning down the disk (stop rotation) – Referred to as Power Saving
Stopped Time on VTrak.
Power management must be:
• Set on the RAID controller. See “Making Controller Settings” on page 70 or
page 167.
• Enabled on each HDD. See “Making Disk Array Settings” on page 128 or
page 184.
Capacity Coercion
This feature is designed for fault-tolerant logical drives (RAID 1, 1E, 5, 10, 50,
and 60). It is generally recommended to use physical drives of the same size in
your disk arrays. When this is not possible, the system adjusts for the size
differences by reducing or coercing the capacity of the larger drives to match the
smaller ones. With VTrak, you can choose to enable capacity coercion and any
one of four methods.
Enable capacity coercion and choose the method in the Controller Settings
menu. See page 122 or page 177. The choices are:
• GB Truncate – (Default) Reduces the useful capacity to the nearest
1,000,000,000 byte boundary.
• 10GB Truncate – Reduces the useful capacity to the nearest
10,000,000,000 byte boundary.
• Group Rounding – Uses an algorithm to determine how much to truncate.
Results in the maximum amount of usable drive capacity.
• Table Rounding – Applies a predefined table to determine how much to
truncate.
Capacity coercion also affects a replacement drive used in a disk array. Normally,
when an physical drive fails, the replacement drive must be the same capacity or
larger. However, the capacity coercion feature permits the installation of a