Digital Equipment Corporation RAID Array 3000 storage subsystem Guide de l'utilisateur télécharger pdf (Page 47)

Chapter 2. RAID Array Controller

EK–SMCPO–UG. A01 2–19

Table 2–6 System Parameters

Parameter Description

Password Checking Enables or disables password checkin

. When password checkin

is enabled, the controller will limit access to certain options unless

the correct password is supplied.

Rebuild Rate Determines how much of the controller’s processin

power is to be

used durin

rebuild operations. A hi

her number speeds up the

rebuild operation, but ma

impact I/O performance. A lower num-

ber will not impact performance, but will require lon

er to rebuild

the RAID set.

Create Rate Similar to Rebuild Rate, but determines the amount of processin

power to be used while creating a RAID set.

UPS Installed Determines whether the controller should enable the UPS warnin

nals (AC Lost and Two-Minute Warnin

). See “Backup Power

Management” for more details.

Read-Ahead Enabled Determines whether the controller should automaticall

pre-sta

data into cache durin

read operations. Enablin

read ahead im-

proves sequential access times as it improves the chance of

et-

tin

a cache hit on a read. However, it is not well suited for random

access patterns since it relies on spatial locality.

Read-Ahead Limit Limits the amount of cache blocks that will be read ahead when

read ahead is enabled. This limit prevents the cache from bein

dominated by read-ahead data.

Validation Delay Determines how lon

the controller will dela

after spinnin

drives before scannin

them. The lar

er the number, the more time

the drives have to initialize themselves.

12-Volt Sensor Enabled Determines whether the controller should monitor the 12-volt input

line.

Host Select WCE Specifies whether the controller allows the host to set and/or clear

the Write Cache Enable bit in the cachin

mode pa

e. Prevents

host s

stems from turnin

write cachin

off and de

radin

per-

formance. See “Write Operations” for more details.

Drive Command Time-out The number of seconds the controller will wait for a drive to re-

select after disconnectin

durin

the processin

of a command. If a

drive exceeds this time, the command will be retried. This value

also indicates the maximum amount of time a drive can be on the

SCSI bus. If a drive is on the bus for a

reater len

th of time, the

drive will be reset and the command will be retried.

Reset Propagation Specifies whether the host channels should propa

ate resets on

other host channels. This is useful in clusterin

environments

where one cluster ma

need to silence the adapter of a failin

peer

cluster.

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Digital Equipment Corporation RAID Array 3000 storage subsystem Guide de l'utilisateur Page 47

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