Seagate ST31230N/ND Guia de Instalação descarregar pdf (Página 241)

Hardware maintenance 16-9

Removing and replacing the disk unit in a shadowed EC 11

Standard 1.0 Option 11 EC Installation and Maintenance Guide November 1999

Removing and replacing the disk unit in a shadowed EC 11

Disk shadowing

overview

Disk shadowing is a process in which the data from one disk

is recorded to a second disk to provide protection against any

loss of data in the event that a disk failure occurs. Shadowing

involves multiple write and alternate read operations. When a

disk error occurs on one disk, the system generates a SEER

and ignores that disk drive; it continues to work with the

other disk drive. In this way, service is not interrupted when a

disk goes down. At the scheduled maintenance time, the

EC 11 is brought down and the disk drive is replaced. Hot

plugging of drives is not supported.

Removing and

replacing the primary

disk

Each primary and secondary disk in a shadowed system is

mounted to a drive plate with a backplane connector. Each

secondary drive plate also contains an auxiliary power supply

for the secondary disk. The secondary disk for Node 1

occupies the lower position in slot 12. The secondary disk for

Node 2 occupies the upper position in slot 12. For a more

complete description of the disk drives including diagrams,

see the “Assembling and installing the disk drives” section on

page 6-3 in Chapter 6, “Installing the disk drives and the tape

drive.”

Dissimilar capacity disks could be used in the same node,

provided the smaller capacity disk is the primary disk with its

SCSI address set to 0. The supplied EC 11 disk drives,

however, are identical in capacity.

The SCSI address for the primary disk in a shadowed system

is 0. The SCSI address for the secondary disk is 2.

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Seagate ST31230N/ND Guia de Instalação Página 241