Users Guide

Controller cache preservation
The controller is capable of preserving its cache in the event of a system power outage or improper system shutdown. The
PERC 10 series controller is attached to a battery backup unit (BBU) that provides backup power during system power loss to
preserve the controller's cache data.
Cache preservation with non-volatile cache
The non-volatile cache (NVC) allows controller cache data to be stored indefinitely. If the controller has data in the cache
memory during a power outage or improper system shutdown, a small amount of power from the battery is used to transfer
the cache data to non-volatile flash storage where it remains until power is restored and the system is booted. If the cache
preservation process is interrupted by power-on, the controller may request an extra reset during the boot to complete the
process. The system displays a message during boot as Dell PERC at Bus <X> Dev <Y> has requested a system
reset. System will reboot in 5 seconds.
Recovering cache data
If a system power loss or improper system shutdown has occurred:
1. Restore the system power.
2. Boot the system.
3. When preserved cache exists on the controller, an error message is shown. For more information on how to recover cache,
see Preserved Cache State.
Battery Transparent Learn Cycle
A transparent learn cycle is a periodic operation that calculates the charge that is remaining in the battery to ensure that there
is sufficient energy. The operation runs automatically, and causes no impact to the system or controller performance.
The controller automatically performs the Transparent Learn Cycle (TLC) on the battery to calibrate and gauge its charge
capacity once every 90 days. The operation can be performed manually if required.
NOTE:
Virtual disks stay in write-back mode, if enabled, during transparent learn cycle. When the TLC completes, the
controller sets the next TLC to +90 days.
Transparent Learn Cycle completion time
The time frame for completion of a learn cycle is a function of the battery charge capacity and the discharge and charge
currents used. Typical time completion for a transparent learn cycle is between 4 to 8 hours. If the learn cycle is interrupted mid
cycle, it begins at a new cycle.
Conditions for replacing the battery
The PERC battery is marked failed when the state or health of the battery is declared bad. If the battery is declared failed,
then all the virtual disks in write-back mode transitions to write-through mode, and the firmware runs learn cycles in subsequent
reboots until the battery is replaced. On replacing the battery, virtual disk transitions to write-back mode.
Operating system device enumeration
Virtual disks and non-RAID disks are presented to the operating system as SCSI devices. The operating system enumerates
these devices based on the SCSI target device in a particular logical order.
The order for PERC H345 is:
1. Non-RAID disks are enumerated first based on the physical device ID.
2. Virtual disks are enumerated second based on virtual disk target ID.
NOTE: H345 non-RAID disks may not appear in slot order.
Features 31