Technologies for the ProLiant ML570 G4 and ProLiant DL580 G4 servers

For more information about SAS technology, refer to the HP technology brief titled “

Serial Attached

SCSI technology”.

Small Form Factor hard drives

SFF drives offer several advantages over 3.5-inch drives. The smaller physical size of the drives

increases the number of gigabytes per U that can be implemented in a server rack. SFF drives have

been shown to be more reliable than their larger counterparts, largely due to the use of smaller parts

and better control of vibration.

Power consumption and heat are also reduced by using SFF drives. SFF SAS drives consume

approximately half of the power used by a 3.5-inch drive of comparable capacity. This reduction in

power consumption gives the added benefit of reduced heat production: SFF drives run cooler than

3.5-inch drives.

Performance also benefits from the move to SFF drives. The smaller platter size results in reduced seek

times as the heads have a shorter distance to travel. RAID performance naturally benefits from having

more spindles; and with SFF, more disks can fit into a given amount of space.

The Smart Array SAS P400 Controller

Both the ML570 G4 and the DL580 G4 include a Smart Array P400 Controller in a PCI Express slot.

This controller offers the benefits of SAS storage and a rich feature set.

Some configurations of the ML570 G4 and the DL580 G4 come with a battery-backed write cache

(BBWC) on the P400 controller. For models that do not come with the BBWC, it is available as an

option. This cache buffers disk writes so that disk I/O can be handled efficiently. The battery is

needed in case of an unexpected shutdown of the system, so that information in the buffer will not be

lost. In the case of a complete system failure, the controller and disks can be moved to a different

server, where the controller will flush out the cache to the disks after power has been restored. In the

case of a controller failure, the cache module and disks can be removed from the failed controller and

moved to a working controller, where the cache will be flushed out to the disks. The battery will last

two days without receiving any power from the computer.

The Smart Array P400 supports RAID levels 0, 1, 1+0, and 5. RAID 6 (double parity) is available and

does require the BBWC. Mirror splitting is available for RAID 1 arrays. This functionality allows the

user to split a RAID 1 mirror into two separate RAID 0 arrays (breaking the mirror). Mirror

recombining is the opposite―combining two RAID 0 arrays into a RAID 1 mirror. The battery-backed

write cache is not required for this feature. For detailed information about RAID, refer to the HP

technology brief titled “

RAID 6 with HP Advanced Data Guarding technology: a cost-effective,

fault-tolerant solution

.”

The battery-backed write cache is required for capacity expansion, which allows the user to add a

physical disk to an existing array. The controller then recalculates parity and balances the data across

the disks. During the expansion, data and logical structures on the array are preserved.

The P400 controller supports a recovery ROM which allows for failing back to the previous good

ROM, in the event of a failed attempt to flash the controller’s ROM. Online Drive Flashing is also

supported. With Online Drive Flashing, disk drive firmware updates can be pre-loaded onto the

controller; and then at the next reboot, the controller will flash the firmware on the hard drives.

Available at this URL: www.hp.com/servers/technology