HP ProLiant DL585 G5 server technology, 1st edition

Storage technologies

The DL585 G5 has an updated disk subsystem and includes the Smart Array SAS P400 Controller.

Serial Attached SCSI (SAS)

The peak data transfer rate for the current generation of SAS drives

is 3 gigabits per second in full

duplex mode. In a serial system, the devices do not share a common bus, and each device can take

full advantage of the bandwidth available to it. The SAS backplane connector is compatible with

SATA drives (although it is not possible to use a SAS drive on a SATA controller), and the chipset on

a SAS controller can communicate with SATA drives. This enables administrators to store data that

needs to be available at a high performance standard on SAS disk drives, and to use the same

enclosure to store data on slower but higher capacity SATA drives.

Smart Array SAS P400 Controller

The DL585 G5 includes a Smart Array P400 Controller which supports SAS storage. Some

configurations of the DL585 G5 include a battery-backed write cache (BBWC) on the P400 controller.

For models that do not include the BBWC, it is available as an option. The battery will last two days

without receiving any power from the computer.

The BBWC buffers disk writes so that disk I/O can be handled efficiently. If there is an unexpected

system shutdown, the battery maintains the information in the buffer so that data will not be lost. In the

event 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 once power has been restored. If a controller fails,

the cache module and disks can be removed from the failed controller and installed on a working

controller, where the cache will be flushed out to the disks.

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. BBWC is not

required for mirror recombining.

The BBWC is required for capacity expansion functionality, 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 that allows for failing back to the previous valid 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.

Networking technologies

The DL585 G5 includes two BC5706i multifunction gigabit Ethernet (GbE) network adapters.

Technologies supported by the BC5706i include TCP Offload Engine, Receive Side Scaling (RSS),

and accelerated iSCSI.

TCP Offload Engine

Network bandwidth has improved steadily since the early days of TCP/IP networking. Along with this

improvement in speed has come increased demand for CPU cycles to manage the network protocol

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

technology available at

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00302340/c00302340.pdf.