User`s guide

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
g
. When password checkin
g
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
g
power is to be
used durin
g
rebuild operations. A hi
g
her number speeds up the
rebuild operation, but ma
y
impact I/O performance. A lower num-
ber will not impact performance, but will require lon
g
er to rebuild
the RAID set.
Create Rate Similar to Rebuild Rate, but determines the amount of processin
g
power to be used while creating a RAID set.
UPS Installed Determines whether the controller should enable the UPS warnin
g
si
g
nals (AC Lost and Two-Minute Warnin
g
). See “Backup Power
Management” for more details.
Read-Ahead Enabled Determines whether the controller should automaticall
y
pre-sta
g
e
data into cache durin
g
read operations. Enablin
g
read ahead im-
proves sequential access times as it improves the chance of
g
et-
tin
g
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
g
dominated by read-ahead data.
Validation Delay Determines how lon
g
the controller will dela
y
after spinnin
g
up
drives before scannin
g
them. The lar
g
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
g
mode pa
g
e. Prevents
host s
y
stems from turnin
g
write cachin
g
off and de
g
radin
g
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
g
durin
g
the processin
g
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
g
reater len
g
th of time, the
drive will be reset and the command will be retried.
Reset Propagation Specifies whether the host channels should propa
g
ate resets on
other host channels. This is useful in clusterin
g
environments
where one cluster ma
y
need to silence the adapter of a failin
g
peer
cluster.