Sun Microsystems Fire 880, Руководство пользователя

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96 Sun Fire 880 Server Owner’s Guide • August 2001
The FC-AL disk backplane provides dual-loop access to all internal disk drives.
Dual-loop configurations enable each disk drive to be accessed through two separate
and distinct data paths. This capability provides:
■
Increased bandwidth – Allowing data transfer rates up to 200 Mbytes per second
versus 100 Mbytes per second for single-loop configurations
■
Hardware redundancy – Providing the ability to sustain component failures in one
path by switching all data transfers to an alternate path
For more information on the RAS and performance capabilities of the mass storage
subsystem, see “About Sun Fire 880 Mass Storage Features” on page 92.
Note – To take advantage of the dual-loop capability of the FC-AL backplanes, an
optional PCI FC-AL host adapter card must be installed to control the second loop
(Loop B). For more information, see “About FC-AL Host Adapters” on page 99.
Port bypass controllers (PBCs) on the disk backplane ensure loop integrity. When a
disk or external device is unplugged or fails, the PBCs automatically bypass the
device, closing the loop to maintain data availability.
Each backplane also includes two integrated SSC-100 SCSI Enclosure Services (SES)
processors, one for each loop. The SES processors:
■
Interpret enclosure service commands from the host software
■
Manage the backplane’s FC-AL loop configuration
■
Monitor status signals from disks and disk backplanes
■
Control disk status LEDs
When a second backplane is installed to form an expanded 12-disk array, only the
SES processors on the base backplane are active; the SES processors on the upper
backplane remain inactive.
Configuration Rules
■
The FC-AL disk backplane requires low-profile (1.0-inch) disk drives.
■
The optional expansion disk backplane is installed above the base backplane.
Note –
All internal options (except disk drives and power supplies) must be
installed only by qualified service personnel. For information about installing or
removing an FC-AL disk backplane, see the
Sun Fire 880 Server Service Manual , which
is included on the Sun Fire 880 Documentation CD .